As KSoD (our resident Windows expert), will tell you, that isn't really true. Vista was only unstable and problematic on release and the first year of its life. It's now a decent and stable OS.
Not that I'm recommending it of course - Windows 7 all the way
Windows 7 will probably be more reliable and get your better performance from an SSD.
Also, Vista 64-bit doesn't support TRIM - TRIM is a thingy that SSDs use to increase their lifespan, and prevent the SSD's performance from reducing over time.