I would avoid the R89C, to be honest, as its lack of competitiveness will most likely frustrate you.
The 88C-V, like many of the group C cars, would be more competitive at a higher HP limit, but you should still have a good time with it.
What's astonishing to me is that on GP/F the R89C was faster than the 88C-V by about 3 hundreths of a second. And on Suzuka, it was faster by 1.9 seconds (probably because I tested the 88C-V first).
But whenever the 88C-V is faster, it's by...
.400, 3.8 seconds, 3.2 seconds.
on Daytona, Spa, and Seca respectively
And on Spa I tested the C60 first so that shouldn't be why the R89C was 3.8 seconds slower.
From what I've seen, the R89C handles like a charm, it's great. But I feel it doesn't accelerate nearly as quickly (although it actually does, or is pretty close from looking at telemetry) or have the same top speed (which again it does). The 88C-V can take high speed corners such as Tetre Rouge and the last long corner in Spa at full speed where the R89C or C60 can't.
I think I've ruled out the C60 at this point.
Just going to do a few tire wear tests, run a few laps on Sarthe in the R89C and 88C-V then grind to buy a 787B and a R92CP if one shows up in my UCD.
Also my impressions on the C60:
It's a boring drive, and it spins out way too frequently even though I drive carefully. I was on my third lap of Laguna Seca and on the second corner it spun out while I was gradually accelerating in third gear. I hit the apex, my steering wheel was pointed no further than for the other cars, and it just spun out.
C60 Hybride = Have a spare wall to punch.