Another common thing people mistaken for. Formatting a hard drive frequently will not in any way shorten its lifespan. How can formatting -- preparing a filesystem has anything to do with reducing a hdd lifespan?

Anyway, back to the topic. Vista SP1 and Server 2008 share the same kernel. Everything from I/O and memory management should be same in terms of performance. Well, of course, if you take into account the features enabled by default on Vista, you would probably say Vista performs slower.