If it's your main computer definitely a Mac. I'll never go back and I run my MacBook Pro into the ground day in and day out (I'm a research scientist, and it does all my number crunching, full res image viewing, etc. on top of the day to day stuff and also doubles as my DVD player so it NEVER gets a break).

However, they ain't cheap (in that they don't make a low-priced model like other companies), so I'd have a hard time buying one as a secondary computer for just email and storage.

I'd either go for a used Apple (maybe refurbished) or get a cheapy and strip it of the Windows nightmare (yes, I'm that anti windows) for a Unix distribution. I've had good luck with HP (back in the terrible days of Windows and AOL), but that was a desktop.