I just looked it up, and according to their site:
Vixen = 150 lb pull, 285 fps, 6.0 lbs, and 37" overall length.
Phoenix = 175 lb pull, 305 fps, 6.3 lbs, and 37" overall length.
Exocet = 200 lb pull, 330 fps, 6.4 lbs, and 38.5" overall length.
If is was me, I would rather have the extra 20 fps even if at the cost of 0.3 lbs or 136 grams. Overall length is the same for the two you are considering.
Personally I am leaning towards the Exocet 200, but most of my hunting will be done in stands or shooting houses.
Thanks,
Nixsrs93