If you have the budget go for the R9, is stronger so in the long run is better, but if you don't have the budget go with the R5 is a good choice too, is reliable and good to use, but maybe in the long run you want mor Nm. Definitely go for what your pocket can handle it.

I have an R5 and don’t find any need to upgrade but getting the R9 future proofs you for a long while and I can’t see more than 9nm being necessary but it’s all personally preference.

I think the r9 is better because you have headroom of force feedback, you can configure the wheel to higher nm depending on what are you playing

R5 is working fine for me.