Both these drives will make excellent operating system drives, they are both so far out ahead of the rest of the MLC pack, as an operating system drive.
Vertex is faster in some areas and Intel is faster in others. I have read the reports on the Intel X25-M writing performance slowing down after the drive has been used for a while. I don't have an Intel drive so i can't comment how bad this is in "real world use". I haven't noticed any slowdown in the OCZ Vertex, but all SSD drives will slow down a little when they are used. Ordinary spinning hard drives slow down as well, until you defrag them.
Of course you should not use "normal" defrag on an SSD drive. But there are new applications, designed specifically for SSD to consolidate free space, such as Disk Keeper HyperFast. This application runs in the background as a service and free space consolidation takes place without you even noticing.
Possibly to much worrying is going on about MLC based SSD slowing down in any case, and people are only looking at benchmarks. Real world use is different matter altogether and both these drives will completely blow away any traditional spinning HDD.
For example (and i have not tested this myself). A single OCZ Vertex will completely blow away 2x WD VRaptors in RAID 0, when used as an operating system drive, and no doubt, the Intel SSD drives will do the same.