Well I can speak on both.
The Spec V in an awesome car and a great buy.(Bang for the buck)It takes curves and on/off ramps like a pro.It has lots of goodies in stock form and there is a growing aftermarket for it.The Spec V is so much fun to drive everyday(I only get to drive mine once a week now if i'm lucky)If you are thinking about a new one though I recomend getting an 02 or 03.I'm not big on the changes they made on the 04.
The Altima is another awesome car.I have the 3.5se in auto form and love it to death.The V6 is a power house and the styling is great too.Mine has the heated leather which I love.The one that I got was a bit pricy but it is loaded and I got it right after the new gen came out.It took me over 2 months to decide between the Maxima and altima and find a Black on Black one.The 2.5 is a good buy too.Rob and Bud have the 2.5 both auto's I think.
No matter what you get between the two I know you will be happy.
Back to topic...I Keep my cars clean too.(well the Black Altima is hard to keep up with but I try)