Which is better? ... in what field? Better in the void mean nothing. What do you want to do with it?

For what I know about this chips, they are both based on the same design, both are good for 2D (DOS & Windows) and both are pitiful for 3D but the ViRGE was sold for it (Edit: meaning it has S3D and Direct3D enabled in the driver).
Except for that, there is surely some difference here and there. But I think the 86C775 is most likely a revision of the 86C375. Of course, I can be wrong and someone with more knowledge will tell us that.
I suppose you are not interested in early 3D games, but with a 3dfx Voodoo your build can be even greater 😉

Trio 64V2/DX has better RAMDAC. Performance won't be significantly different between them.

Wasn't the Virge/DX the 375 revision number and not 325? Anyway if I'm correct the Virge/DX should be more complex (for what it matter) as a gaming oriented early 3D (and good 2D) accelerator while the Trio64V2/DX was still a good 2D only accelerator, same RAMDAC clock but from specs that should be better in the Trio64V2 (while I suppose the output quality will depend as usual by the manufacturing quality of the whole card/brand). Edit: I thought the Virge/DX also had some MPEG1 acceleration but not.

Didn't noticed Virge DX in the title. Oh well, yes, they have identical RAMDAC, but in ideal scenario Trio 64V2/DX is slightly faster anyway: PCI Video cards benchmark: Electric Boogaloo Edition

Compared cards in the flesh: Re: Graphic card memory speeds

Keep in mind that any improvements on PMMX200 will be from minuscule to none. And built quality and clocks between different brands varied noticeably.

I'd say the main advantage of S3 ViRGE/DX over its 2D-only counterpart is the hardware support for API (S3D)-exclusive games - such as Terminal Velocity <3 Also Destruction Derby, FX Fighter Turbo, Havoc and Screamer.

After some overclocking anyway.