Vick's release (besides having the glitch happen during) was kinda poop needing a lot of AP to become a mobile passer. He's another AP sink like Big Truzz but without Truzz's release and ease of movement. I'm very disappointed with the card, you either need to build him for a pocket passer or give up a huge chunk of your team's AP.
Allen is a terrific card. You can build him into the Allen you see every Sunday/Monday/Thursday/and Saturday during the playoffs for 4 AP. He has a nice short to middle game with a better deep ball than Vick or Rodgers. He's 800 pounds and 6'5 with 90 carry which means he's difficult to take down and can break it for a TD if he breaks through initial contact. Allen's problem is his price is just going to keep going lower, I predict he'll be mid 600k tomorrow and no one wants to overpay for a player.
While Vick and Allen are fleeting, Sandcastles are forever. Routinely found for 350k, Leon Sandcastle is one of the best values in MUT history. He's clutch, he's fast, he has Slinger 3 with Gunslinger which gives him the best deep ball in the game and short to middle with zip, he needs 5 AP to be his best. He can even run but dear God you better slide or his spine is going to pop out of the top of his head.
Leon Sandcastle is the best premier QB currently in the game without any major downsides.