Compared to OTV3, nemesis is better if you're just looking at how it performs. It has a better resolver, better doubletap and imo better anti-aim.
However, compared to nemesis, OTV3 has so many more features that nemesis is missing: buybot, knifebot, instant skinchanger, lua or js, etc... If you want to be able to customize everything you could ever want, go for OTv3 but don't expect it to perform as well as nemesis would.