What’s the difference between the hexagonal Trigon and the square Blokus? Well, there is an extra piece (22 vs. 21) in Trigon, and the shapes, though similar in variety to pentominoes, are built of triangles as opposed to squares.
But the rules are basically the same. And the play is basically the same. And both games have variations for 1-4 players (yes, solitaire versions, of significantly enticing challenge, I might add).
I can only think of one significant difference – a purely visual one, which, my friend, is more than significant enough. Since so much of playing Blokus depends on the ability to perceive shapes, changing from a square to a triangular unit makes all the difference. Even for a Blokus master, Blokus Trigon is a whole new game.