Windows 7: Best SDHC or Micro for System use: Boot, tools, installs?

I have a motley crew of oddball SD's and Micros, some high capacity some not. so far I have not seen one that would just flat fail in system chores, but I am wondering: what brand/part, or what Spec do you experts look for in such items?? I'm sure some are faster than others, and perhaps some more durable for lots of wipes/rewrites, storage of boot records, etc? I need to get a couple of higher capacity ones and wanted some advice before ordering.

thanks!

My answer is probably not quite what you are looking for, but I mostly just look at brand and price. I usually buy a SanDisk card because I'm familiar with the brand name and their usually a little cheaper than camparable Kingston cards. I've also only ever had one stop working in 6 years of buying them. Basically, if I haven't heard of the brand I stay away from it. since you asked about speed, below is a link to a wikipedia page that discribes the how the different speeds are catagorized for SD cards.

Secure Digital - Wikipedia, the free encyclopedia