Well firstly, you say whether to go 15K SCSI or Raptor, and later you ask about RAID0 Raptor vs SCSI. Are your options RAID0 Raptor or a single SCSI drive, or do you want to know about single drive Raptor performance too? And also "15K SCSI" definitely needs to be better defined, the various 15K SCSI drives perform VERY differently under different workloads.
Anyways, answers to a lot of what you asked can be found here, and on the next page of the review:
http://www.storagereview.com/articles/200601/WD1500ADFD_4.html
As you can see, for single-user scenarios the Raptor is just plain faster a majority of the time. Why? Well because 15K SCSI are built with workstation and server use in mind, and as such a lot of the focus is on seek times. However, in a single-user scenario this is largely negated because the workload is very different. Plus, a HUGE difference comes from the drive firmware, where again the SCSI drives are targetted towards a completely different use. Again you can see this in the review, forgetting the Raptor for a moment look at just how varied the performance of the 15K SCSI drives is - and all this is despite the fact that many of them have very similar read speeds and access times. Another myth you need to forget is that fast reads and writes directly transfer to faster single-user performance. For this you can check out the 15K.5 Cheetah review:
http://www.storagereview.com/articles/200609/ST3300655LW_1.html
As you can see the transfer rates of this drive are truly unparalleled. It's just a monster. However later when you take a look at the single-user benchmarks you'll see that it doesn't do well AT ALL, including against previous-generation drives. On the other hand the one thing I will say that the SCSI drives have going for them is that with prolonged use your OS, pagefile, etc will get more and more fragmented. As that happens, the seek times will start to play a larger role since your drive will have to more and more seeking. I think this might be one of the reasons why some people end up saying that the SCSI drives are faster, or alternatively it's just a psychological effect of "OMG 15000 RPM".
Also you say cost isn't an issue but clearly it should play at least some role. To get a SCSI card and a SCSI drive you'll almost definitely pay more than a single Raptor (this is considering ebay prices, if you buy a SCSI card at an online retailer or whatever it's gonna cost an arm and a leg, or a kidney!). Another point of consideration is whether your data is important to you - RAID0 Raptors will have a considerably higher chance of failure than a single SCSI drive. I've never seen a RAID0 vs single SCSI benchmark for single-user use, and I doubt you'll find one cause it isn't exactly fair, but I'd be willing to bet anything at all that they would crush the SCSI drive (any SCSI drive) completely.
Sorry for how long that got but hopefully it helps you out.
Anyways, answers to a lot of what you asked can be found here, and on the next page of the review:
http://www.storagereview.com/articles/200601/WD1500ADFD_4.html
As you can see, for single-user scenarios the Raptor is just plain faster a majority of the time. Why? Well because 15K SCSI are built with workstation and server use in mind, and as such a lot of the focus is on seek times. However, in a single-user scenario this is largely negated because the workload is very different. Plus, a HUGE difference comes from the drive firmware, where again the SCSI drives are targetted towards a completely different use. Again you can see this in the review, forgetting the Raptor for a moment look at just how varied the performance of the 15K SCSI drives is - and all this is despite the fact that many of them have very similar read speeds and access times. Another myth you need to forget is that fast reads and writes directly transfer to faster single-user performance. For this you can check out the 15K.5 Cheetah review:
http://www.storagereview.com/articles/200609/ST3300655LW_1.html
As you can see the transfer rates of this drive are truly unparalleled. It's just a monster. However later when you take a look at the single-user benchmarks you'll see that it doesn't do well AT ALL, including against previous-generation drives. On the other hand the one thing I will say that the SCSI drives have going for them is that with prolonged use your OS, pagefile, etc will get more and more fragmented. As that happens, the seek times will start to play a larger role since your drive will have to more and more seeking. I think this might be one of the reasons why some people end up saying that the SCSI drives are faster, or alternatively it's just a psychological effect of "OMG 15000 RPM".
Also you say cost isn't an issue but clearly it should play at least some role. To get a SCSI card and a SCSI drive you'll almost definitely pay more than a single Raptor (this is considering ebay prices, if you buy a SCSI card at an online retailer or whatever it's gonna cost an arm and a leg, or a kidney!). Another point of consideration is whether your data is important to you - RAID0 Raptors will have a considerably higher chance of failure than a single SCSI drive. I've never seen a RAID0 vs single SCSI benchmark for single-user use, and I doubt you'll find one cause it isn't exactly fair, but I'd be willing to bet anything at all that they would crush the SCSI drive (any SCSI drive) completely.
Sorry for how long that got but hopefully it helps you out.