the one way is heavier than the standard diff.
All of the bearings will be light, relatively the same weight. If you have one of the newer kits, then you have steel shielded bearings and they are as good as any unless you wanna go ahead and spend $100 USD on a set of ceramic ball bearings.
Senna: just some advice: I think you are concerning too much with some things that really will improve your performance very little. The track you talk about seems to be very large where acceleration out of corners should not be a concern but your biggest concern should be keeping the speed that you have and carrying through those big turns and that big track that you talk about. We have many drivers at our track of all skill levels and we all interact with one another and share information (for the most part) and I will tell you that even with the same equipment, same cars, same setup, all things being equal, I can give my car to one of the less experienced racers and I can drive his and I will still be faster than he is. Once you become a better drive then it is when you might want to search for every possible edge possible. Right now, you should just practice, practice, practice.