This may not be new news to anyone, I'm not sure, but I had the opportunity to speak with one of the guys recently that was working on the project with them. Turns out that Tetrisphere really is a'bit of a different game than what was originally being made for on the Jaguar. Some things to highlight or note:
-Game play on the Jaguar version is bolder and simpler, which makes it more entrancing and faster-paced than Tetrisphere.
-It uses all flat-shaded polygons and the frame rate was always about 60.
-The game play is faster on the Jaguar because you could not/did not produce 'combo chains' or drag pieces around, you just focus on moving the sphere to align with the current piece. Part of the reason this changed for the N64 is because the producer, who was of Killer Instinct fame, seemed to be obsessed with 'combo' move game play. As a result, the game play has to be slower as a result to provide enough time to move pieces around to align before dropping a piece. It takes away from the core mechanics a bit. Also, since it became a more complex game, it almost couldn't be played without some sort of explanation to a new player where as on the Jaguar version, you can just pick it up and go!
-Graphics - the textures got a bit noisy and heavy on the N64 - there is something much punchier and clear about the flatter style of the shaded polygons for the Jaguar version.
-The team continued working on Jaguar stuff for a bit during the development of Tetrisphere but more because it was a pet fascination given the imperative to ship Tetrisphere. They had a very interested and talented programmer at the time that found the Jaguar to be really powerful for making sprite based games but felt it was oversold as a 3D platform - they kept experimenting but never settled or committed to anything else.
-Music was done in XM format ( fast tracker ) and was roughly around 75% accurate and sounded all kinds of messed up. Soundtrack would have been very similar to what was in Tetrisphere but more constrained in terms of number of voices due to cartridge rom size. XM could have up to 64 channels vs MODs being limited to 4.
Maybe said person I spoke with may find their way here to further elaborate and share even more detailed experiences/memories.