Short answer is Voodoo 1 has better compatibility with early glide games, although there are patches for some of them to allow them to run on other 3dfx hardware (Uprising 1.05 comes to mind). But it's SLOW. You get "cinematic" frame-rates in most games for example, on my Compaq Despro 2000 (200MHZ pentium non-mmx) Quake 2 is only playable @512x384 - gl-quake is playable most of the time at 640x480 but it has slowdowns. Uprinsing runs at around 24-28 fps. Playable, but not enjoyable. On my Dell GX1 (333Mhz pentium 2) quake 1 is fully playable, quake 2 is playable(ish) @ 640x480 and uprising is very smooth but it will sometimes crash to desktop (CPU too fast?).
The voodoo 2 on the other hand seems to take some load off the CPU, so in my pentium 200, everything is butter-smooth even at 800x600 in most games, but some older games like pandemonium!, the original DOS carmageddon 3dfx patch, Uprising Join or Die (unpatches) and Tomb Raider (unpatches) will not run on it.
I'd say an 8mb voodoo 2 is a better match for a pentium 233MMX - it provides a much smoother experience. The voodoo 1 is just plain slow - my opinion. Maybe I've been spolied by modern hardware and constant 60fps....
There is another option... for the price of a voodoo 2 you might be able to find a PCI voodoo banshee - that gets you 2 birds with one stone. It's got an excelent 2d core with great dos compatibility, and it performs much faster then a voodoo 1 in glide. It't not as fast as a voodoo 2 but close, and it supports higher resolutions in games - like 1024x768 and higher in glquake. On a 450MHz pentium 2, a banshee can handle quake 2 @ 1024x768 fluently if you turn on 8 bit textures.