I did a basic DOOM framerate benchmarks here.

Difference of about 2fps between Virge VX/DX and Voodoo 3 PCI.

Compared to Voodoo 1, Voodoo 3 has superior quality and cleaner output and less noise on the monitor. No need for a separate 2D card. If you ask me, it doesn't hurt to put the Voodoo 3 in the P133 system. Workarounds/patches for older Voodoo1/2 games may be available for using with the Voodoo 3, but otherwise, generally, it's okay with most games.

Malik wrote:

Difference of about 2fps between Virge VX/DX and Voodoo 3 PCI.

Thanks for this information. To clarify this statement for those who don't click that link, the Voodoo3 in Malik's test was about 2 fps faster in DOOM than the Virge DX.

my Voodoo 4 4500 is kind of not ideal on DOS, it gives me some artifacts with many 320x200 games I think (higher res seems fine), not sure if it's just the combination that I have (440BX, V4 PCI) or what, but it would make me worried about using a Voodoo for DOS

feipoa wrote:

What is the DOS speed difference between a PCI S3 Trio or Virge and a PCI Voodoo3?

That will depend on the game, the video mode used, the CPU (is it a bottleneck?), and if you are using performance enhancing tools for the S3 (s3vbe20/s3spdup, potentially even mclk).
There are some comparisons on http://www.vgamuseum.info/index.php/benchmarks, but those use a faster Athlon XP so there is practically no CPU bottleneck.
I agree that a PCI Voodoo3 is a very good performer in DOS, but those are not common so it is kind of wasted in a slow Pentium. I would probably use one with a faster CPU (at least a faster K6-2 or P2/P3) if the board doesn't have AGP, the AGP slot has compatibility issues with a Voodoo3, or you want to use it alongside another (probably more powerful) AGP card.