Fight? Of course AJ. But RD is also good in fighting, it is one of her hobbies. AJ is honest brute but RD is michievous tomboy, they have connection one another. Both of them have an enhanced strength, athleticism, speed, and good durability. The difference is in the way they practice their strength and ability. OK, RD is swifter, faster, and agiler but AJ is stronger and fights with a cleaner way. Both of them are competitive that make them become the best fighter out of mane 6 physically (without magic). We cannot judge someone if we don't see it immadiately, this is only the opinion of who is our more favorite but we will never know who will win in a fight. Go AppleDash