I don’t have BOTB, but I did buy AAG for my son and we enjoy it.
I would be surprised if most folks in this forum did not say AAG is better. I definately think it is worth the cost. It is a much different game from AAR, AAP or AA50. As a matter of fact, we joke about AAG that to learn how to play it, you have to forget how to play the other AA games. Happy rolling. BTW, if you are interested in enhancing your AA experience, check out the Field Marshall Games company where you may buy custom AA dice. You may find more info in the “Variants” forum here at A&A Org.