Well after doing some testing ( Offline ) the difference between BTB: CTF and Arena: CTF is the following:
-
BTB: CTF = You get both Weapon Drops and Vehicle Drops via Pelican and Flag is caped at a different place where you picked up the flag from.
( That kinda sucks.) example: Maps Hightower and Fragmentation. -
Arena: CTF = You only get Weapon Drops ONLY!! and the flag is at your base
I am a Halo traditionalist 
I like BTB: CTF but when we get “FORGE” I will make sure the flag will be at the same place at
where you see it and cap it at. Not at two different places!
And lots more stuff ! Just wish we had some Docs so we know what does what in the Game Modes!