RedJaron
Splendid
@Kittle
I think you're heading into full on system component selection, not just mboard. Such a thing would result in a very long article and would be better reserved for a series of articles. That said, I do think there needs to be some consideration about how the different parts will work together ( beside actual platform compatibility. )
@Onus & Crash
Tom, I think Onus is saying you've covered the "what" very well in the details ( and as Meteor said, I think the detailed chipset comparison is very useful, ) but new users could benefit from a "why." Just as you said, those of us that are well-marinated in tech pools sometimes forget what it's like to take that first dip. Why would they care about SATA II vs SATA III and the number of each available? Why would they care about PCIe lanes available? Why would they care about two RAM slots or four? What is a RAID and why would someone a controller for it? Is USB 3.0 good enough for you, or do you want eSATA too?
Here are a few things I'd address "why" when a first-timer is picking a mboard, apart from the obvious CPU and RAM compatibility. Some have already been brought up. Keep in mind I approached this as someone advising a tech-neophyte on his first system build. As such, I'm assuming they aren't asking for a high-end build. I suppose it is possible you could have a power-user with very high and/or specific performance needs that doesn't know how to assemble a computer, but I'm not addressing that corner case.
Size
Not only the dimensions and slot count of ATX vs mATX vs ITX, but why you might want one of the boards over another ( mATX tend to be cheaper and are great if you don't plan on many cards, ITX for absolute smallest machine, etc. ) I'd also address what cards are typical in certain computer use cases. A new user might think they need every slot possible "just in case" they need it in the future only to find three years later they still haven't used any.
I/O Ports
USB - How many ports do you really need? The way I see it, rear ports are for things that plug in once and stay ( printers, scanners, keyboards, etc. ) You shouldn't be constantly reaching around back to swap things out. If you are, you either need a hub ( on the desk or monitor, ) or more front-panel jacks ( case. ) This means you might want to look at internal headers too and whether they'll work with the case you have in mind. Remember that peripherals don't take advantage of USB 3.0 bandwidth so don't freak out too much if you only have two 3.0 ports.
Video - If you're not using a dGPU, does the mboard have the right video jacks for your monitor(s)?
Audio - Don't worry too much about multi-channel audio or fiber optic /digital coax jacks if you're just using some $30 stereo speakers. Fewer audio jacks doesn't necessarily mean poorer audio quality.
Memory Connectivity
Do they need four RAM slots, or will two suffice?
Explain basic difference in speed between SATA II and SATA III. The vast majority of machines can get by with four SATA ports ( really even two for home and office use. ) I'd also explain that having only two SATA III ports and the rest at SATA II is nothing to worry about unless they plan to use nothing but SSDs. What about eSATA? People coming from older machines may not have USB 3.0 capable external drives. Even if they do, eSATA has some advantages since you can boot from it. I'd also explain how eSATA usually shares with one of the internal SATA ports.
Legacy Support
I can see this particularly useful for people upgrading from a very old machine. Do they need old parallel or serial ports for old dongles? Any old PCI cards they still need? ( doubtful, but you never know for sure. ) What about old PATA drives? ( though really any old data should be transferred over to SATA drives. ) I'd explain that older cards and devices in their old machine ( sound cards, drive & network controllers, ) are likely unnecessary to carry over to the new machine since the integrated parts in the mboard are superior to the older tech.
I think you're heading into full on system component selection, not just mboard. Such a thing would result in a very long article and would be better reserved for a series of articles. That said, I do think there needs to be some consideration about how the different parts will work together ( beside actual platform compatibility. )
@Onus & Crash
Tom, I think Onus is saying you've covered the "what" very well in the details ( and as Meteor said, I think the detailed chipset comparison is very useful, ) but new users could benefit from a "why." Just as you said, those of us that are well-marinated in tech pools sometimes forget what it's like to take that first dip. Why would they care about SATA II vs SATA III and the number of each available? Why would they care about PCIe lanes available? Why would they care about two RAM slots or four? What is a RAID and why would someone a controller for it? Is USB 3.0 good enough for you, or do you want eSATA too?
Here are a few things I'd address "why" when a first-timer is picking a mboard, apart from the obvious CPU and RAM compatibility. Some have already been brought up. Keep in mind I approached this as someone advising a tech-neophyte on his first system build. As such, I'm assuming they aren't asking for a high-end build. I suppose it is possible you could have a power-user with very high and/or specific performance needs that doesn't know how to assemble a computer, but I'm not addressing that corner case.
Size
Not only the dimensions and slot count of ATX vs mATX vs ITX, but why you might want one of the boards over another ( mATX tend to be cheaper and are great if you don't plan on many cards, ITX for absolute smallest machine, etc. ) I'd also address what cards are typical in certain computer use cases. A new user might think they need every slot possible "just in case" they need it in the future only to find three years later they still haven't used any.
I/O Ports
USB - How many ports do you really need? The way I see it, rear ports are for things that plug in once and stay ( printers, scanners, keyboards, etc. ) You shouldn't be constantly reaching around back to swap things out. If you are, you either need a hub ( on the desk or monitor, ) or more front-panel jacks ( case. ) This means you might want to look at internal headers too and whether they'll work with the case you have in mind. Remember that peripherals don't take advantage of USB 3.0 bandwidth so don't freak out too much if you only have two 3.0 ports.
Video - If you're not using a dGPU, does the mboard have the right video jacks for your monitor(s)?
Audio - Don't worry too much about multi-channel audio or fiber optic /digital coax jacks if you're just using some $30 stereo speakers. Fewer audio jacks doesn't necessarily mean poorer audio quality.
Memory Connectivity
Do they need four RAM slots, or will two suffice?
Explain basic difference in speed between SATA II and SATA III. The vast majority of machines can get by with four SATA ports ( really even two for home and office use. ) I'd also explain that having only two SATA III ports and the rest at SATA II is nothing to worry about unless they plan to use nothing but SSDs. What about eSATA? People coming from older machines may not have USB 3.0 capable external drives. Even if they do, eSATA has some advantages since you can boot from it. I'd also explain how eSATA usually shares with one of the internal SATA ports.
Legacy Support
I can see this particularly useful for people upgrading from a very old machine. Do they need old parallel or serial ports for old dongles? Any old PCI cards they still need? ( doubtful, but you never know for sure. ) What about old PATA drives? ( though really any old data should be transferred over to SATA drives. ) I'd explain that older cards and devices in their old machine ( sound cards, drive & network controllers, ) are likely unnecessary to carry over to the new machine since the integrated parts in the mboard are superior to the older tech.