One major difference between the brands is whether they can mount on
joists that are 16" on center, or need 12" on center. Trex IIRC
requires 12". I did find one brand locally that used 16", this was
quite important for me since I was using the existing deck structure
(which was 16" O/C). If you are building all new, 12" just adds a few
extra joists which may not be that big a deal.
Most of the rest is up to you, what you want for finish, texture,