When the Voodoo2 was first released, it was available in two memory configurations, an 8MB and a 12MB configuration. The same discussion took place over which was the better option of the two, from a price/performance standpoint. The final result ended up being that the 12MB configuration was better overall for the long run. The reason being that although Quake 2 demo1.dm2 scores proved the 8MB to be generally as fast as the 12MB card, during real world gameplay, especially during network deathmatch games, the 12MB Voodoo2s extra memory came in handy when preventing texture swapping due to a lack of local memory.
Texture swapping has been less of a problem in recent times due to the proper implementation of the AGP specification in the latest graphics accelerators. What happens when a card is forced to "swap" textures is that the amount of local graphics memory (on the card) is not enough to accommodate all the textures being loaded at any given time, therefore the textures must be stored in system memory. When dealing with older graphics cards this storage and retrieval process takes place via the 33MHz PCI bus, which ends up allowing for approximately 133MB/s of memory bandwidth. While that may seem like a lot, compare it to the 2400MB/s on the slowest TNT2, so long as those textures remain in its 16MB or 32MB of local memory. AGP 2X makes things a bit faster, upping the performance to 533MB/s, however it's still not even half as fast as accessing the local memory on the slowest TNT2.
The moral of the story? You can run as many benchmarks as you want comparing 16MB to 32MB, and some will tell you that 16MB cards perform just as well as 32MB cards, while others will say the exact opposite. The truth of the matter is, with 32MB of local graphics memory on your TNT2, there is less of a chance that you'll be going to system memory for texture storage retrieval than with 16MB. The better overall decision, from a performance perspective, is to go with a 32MB card, the price difference between 16MB and 32MB cards simply isn't enough to justify going with 16MB.
It wouldn't be too surprising if the 16MB TNT2s disappeared just like the old 8MB Voodoo2s did not too long ago