I've created several post-MKA games, and we like the characters Mortal Kombat, therefore I'll tell you the exclusive character of characters already existing and how many new comers each of the four choices have and you choose which one you like the most.

Option A:
31 Characters (28 Playable w/ Sub-Boss and Boss w/ an extra boss if provided that you completed arcade mode w/out continuing)
14 New Characters
Exclusive Characters: Liu Kang, Stryker, Motaru, Kai, and Blaze

Option B:
30 Characters (28 Playable w/ Sub-Boss and Boss)
9 New Characters
Exclusive Characters: Kano, Shao Kahn, Jade, Quan Chi, Tanya, Hotaru, Tremor (form MK: Special Forces), and Jerrod (Legendary King of Edenia)

Option C:
30 Characters (28 Playable w/ Sub-Boss and Boss)
7 New Characters
Exclusive Characters: Raiden, Sektor, Noob Saibot, Hsu Hao, and Daegon

Option D:
26 Characters (25 Playable w/ One Character that's the boss then morphs into a strong boss)
5 New Characters
Exclusive Characters: Goro, Mileena, Smoke, Sindel, Sheeva, Ermac, and Frost

FYI: If your favorite characters aren't listed in Exclusive, they're most likely in some if not most of the games the characters that are not in any of the games are Shang Tsung, Kintaro, Kabal, Cyrax, Jarek, Bo Rai Cho, Mavado, Moloch, Shujinko, Ashrah, Kobra, Darrius, Kira, Onaga, Meat, Mokap, Chameleon, and Khameleon.