Don't use vista ,it has many security issues, i guess xp would be a better option. But if you have tried mac before than it would be fine, but if not than it may take your time to see what exactly mac is. It is totally different than the others. Options are ours, decision is yours.
definitely mac. looks more profession on a business presentation with a mac, than any other laptop. Imagine someone coming to a presentation with a red/yellow laptop
I think MAC books look more professional rather than DELL, I use dello Studio XPS and that made me crazy with windows 7 and windows vista both, and when i move to Macbook, it smoothers than ever laptop I used in my life.. MACBOOK rocks.
If you have any slots i'd upgrade you RAM a little. Other then that your good with your Dell, dont get a Mac