Couple of points:
The Altima is now a much larger car than it used to be. It's actually larger than the current Maxima, and it has a cavernous interior for the midsize class. Nissan really wanted to make a change with this car because of the slow sales of the previous Altima, so they COMPLETELY redesigned it, basically from the ground up.
The Altima has also been among the top-rated sedans in its class by JD Power in both
Initial Quality (#1) and
Vehicle Dependability. It was voted the 2002 North American Car of the Year. The 3.5SE also has one of Ward's Auto's 10 Best engines for 2002, and the 4-banger in the 2.5's puts out a decent amount of HP and torque.
That said, there are a number of reasons for you to consider an Accord.
First, there is good ol' brand loyalty!

As you know, the Accord is a great car.
Second, it is yet to be seen how the resale value of the new Altima will turn out, but historically the resale value of a Honda is usually much better than that of a Nissan. However, this is the last year of the current Accord design, which means resale values on 2002 Accords will be somewhat worse than usual.
Third, this is the first year of the new Altima, so there may be a few things they need to fix. I have heard a few complaints on Nissan boards about some fairly obvious cost-cutting in the interior.
If I were you, I would just go test-drive the heck out of both of them, and some of their competitors too. Go over them with a fine-toothed comb. I think there is a lot to be said for either car, but your opinion is the one that truly matters!
