AJ... she is just so adorable and awesome... RBD isn't among my fav ponies anyway, so this was an easy choice...
If I had to choose between the two I would go with Applejack, I prefer her old overall more well rounded personality, and good old fashioned southern wisdom, as opposed to RD's impatience and occasionally overly jockish attitude. And like AJ I too am a southerner, and can be fairly stubborn at times, lol.
Applejack without a thought. Her honesty and selflessness are what I look for in a friend the most...<'3
Applejack's only flaw was that she was stubborn and wouldn't ask for help. However, in "Super Speedy Cider Squeezy 6000", she willingly accepted help from her friends. Which means Applejack's character is perfected, so no more Applejack episodes. But I'm sure the writers will think of something.
Im going with the Cowgirl here. This country-slang (is that even right?) made me decide i like her most.