I need help for these military Army branches please.?

Hey every one, my grandfather was on the delta-force team when he was in the military, and my father was a ranger. I feel that i should be the next in the family line to do something, so i was going to take into consideration in ATTEMPTING to be a ranger, now both my grandfather and father are dead, they died when i was younger so i never got to ask them on advice about this type of stuff, all i really know is that delta-force deals with like terrorism stuff, right? and rangers are like fast deployable top notch combaters? im 18 and i have been giving this alot of thought, which branch is harder to get in between them two? now i know basic training is hard, duh, typical. but which BT between them two is more complicated? and what do you do between these two BT? And when i try to join the military if i score high enough can i jump straight into one of these branches (into training that is?)