Can't say for non-BOP performance, as I mostly only drive these cars in the FIA, but basically you can divide the Gr.1 class into 3 further subclass each with their own strength/weaknesses:
1) Modern hybrids
- Best handling, easiest to drive, great braking and acceleration due to hybrid boost
- Poor top speed and front tyre wear can be an issue due to front hybrid deploying
- R18 is usually fastest but power oversteer can be an issue
- In fuel limited races TS050 is king
- TS030 can be a dark horse in tracks with long corners (e.g. Interlagos) because the R18/TS050/919 doesn't deploy its hybrid unless the wheel is <45 degrees
2) VGTs/modern non hybrids
- Intermediate handling & ease of use
- Lacks acceleration compared to hybrids but makes up in top speed
- Tomahawk, Alpine and LM55 are the trinity here. The pendulum has swung a few times depending on BOP changes, fuel/tyre and track, but currently Tomahawk seems to have the edge
- Tomahawk especially good on tracks with long flowing corners (e.g. Tokyo South, Kyoto Yamagiwa) and very good on fuel
- LM55 is probably the best Gr.1 in terms of tyre saving
- Old R18 and Pug 908 can be fast too in right hands, but their ultimate pace isn't quite as good as the above due to higher tyre wear
3) Group Cs
- Poor handling and brakes compared to the modern cars, slow shift speeds but has the highest top speeds
- Save these for ultra high speed tracks (e.g. Tokyo East, La Sarthe No Chicane)
- R92CP is comfortably the fastest (the others might have a chance if PD actually set their gearbox properly

)
4) Meme class
- Nismo GT-R LM
- Avoid unless you're just racing for lulz
Also some extra tips how to get the best out of the hybrid system here:
https://www.gtplanet.net/forum/thre...th-audi-r18-hot-to-use-kers-correctly.391010/