I own both systems. It really is no contest, the N64 beats the Jaguar in terms of software, and from looking at the games power also. I feel that we don't even know what the Atari Jaguar can do as far as power is concerned. I don't think the people that controlled Atari at the time knew what to do with it. If it is a 64-bit system, by looking at existing games, then it is more of a 64-bit architecture and not a true 64-bit machine. It didn't stay in the game long enough to have a chance. I like my Jaguar, but there are only a hand full of games (counting on one hand) that make it worth owning.
The N64 library is filled with great games and a ton of fun. Over 400 games total and there are a lot of must have, must play, high quality gaming.