I don't think I'd ever consider buying a brand new car just to put 25k miles a year on it. IMHO, that's just a dumb monetary decision.
Buy a year or two old car that's already taken a depreciation hit. Hell, I bet you can find some nicely loaded '01 maximas with under 20k miles on them for ~17k-19k. Figure in your trade in value and you're looking at 14k-15.5k for a car. Not too bad.
As for a warranty...woopdeedoo. You'll be out of a factory warranty in 18 months at that rate. If it's a big concern, you can pick up an aftermarket warranty to last you another 5 years, 100,000 miles for ~$1,000. Even with the extra warranty, you'll still be thousands ahead of buying new.
If you look at '00 or '01 GTP's, you can find those for dirt cheap. I've seen nicely loaded ones here go for under 15k. With your trade in you'll be spending half the $$ as buying new.
If it was me, and I new I was going to be traveling that much, THE LAST thing I'd do was buy brand new. As for which one to buy, I'll tell you right now that the Maxima will age better. GM's in general just don't age well from an intererior standpoint.