Honestly, the built in storage compartments are the only reason that I wouldn't consider a Star. These may be a dryish pocket to hold some dry gear or something but, make it impossible to drop a cooler or something larger into that space.Slice has the benefit of extra storage in the front and rear pockets.
Phatcat is shorter and narrower, making it a bit less stable than the Slice XL, but a bit more maneuverable. Probably not so much that you'd notice the difference.
Phatcat has a much better color selection.
Honestly, can't go wrong either way!