Are micro atx motherboards weak

Solution
a friend of mine uses a 4440 and a 270 paired with an MSI b85m e-45 and it has worked fine for a year and the VRM's went through 6 months of an overclocked G3258. still works flawlessly to date. cheaper board usually will ditch higher end audio, SLI/XFire support, overclocking, and overall better quality components. as long as you dont expect a whole lot from it it should do just fine
a friend of mine uses a 4440 and a 270 paired with an MSI b85m e-45 and it has worked fine for a year and the VRM's went through 6 months of an overclocked G3258. still works flawlessly to date. cheaper board usually will ditch higher end audio, SLI/XFire support, overclocking, and overall better quality components. as long as you dont expect a whole lot from it it should do just fine
 
Solution
As long as you get it from a decent manufacturer, then the only real difference is features. You will have less PCI slots, etc. As long as it has enough slots for what you need you will be fine. Those "console" style pc's, such as steam boxes and the like, use those small mobos and work just fine.
 
It depends entirely on the manufacturer. A matx board is not inherently lower quality, but if the manufacture uses substandard parts then it's crap. If you can tell us which one you're looking at we can give you some opinions or facts about it.