it comes down to what you want to use your bike for. I have both the Bati 801 (The regular is better than the RR) and the Akuma fully upgraded.
Handling: The Akuma seems to be more responsive and turns faster for me but the Bati doesn't handle bad at all. Its a matter of preference here and I prefer the Akuma's handling.
Top Speed: Akuma 140.8 - Bati 801 196.99 I had a top speed of 140.8 with the Akuma for a long time then after racing with the Bati I reached the 196.99 that I have now. You must do a wheelie to go faster on the Bati though.
Acceleration: The Akuma will beat the Bati off the line no matter what you do. The akuma doesn't seem to lose speed on turns either unless you let off the gas. The Bati however if using a wheelie will eventually pass the Akuma on straight aways due to top speed.
My Choice: I use the Akuma for Racing and the Bati in free roam. The Akuma is almost unbeatable in a race and the bati is so much more fun in Free Roam jumping over random small walls and doing backflips in random places.
It comes down to choice and either is a good choice. If you can get used to riding wheelies everywhere then the Bati is the bike for you. If you like going top speed and staying there then go with the Akuma. I need to lose one of them to make room for my last car (Blista) so I can have my fav car from each class but I can't decide which I want to keep (mostly b/c the bati is too much fun in free roam). Hope this helped you make your choice.
For those debating mods: They do affect races by a lot. A stock bike will not even keep up with my Akuma or Bati. When in free roam or LSC the accel bar is maxed on both but in the race selection the Akuma is higher on Accel than the Bati. For some reason when you go into races the real stats show and are lower than in free roam or LSC.