if you are just going to cruise around in flat water and choppy water 3 straps are probably fine
to race 4 straps will probably be faster if you know how to ride a race board
on a wave 2(or 0) straps will probably be better so you can get your front foot across the midline of the board to make the toe side turn effectively. you don't see surfers riding the outside edge of the board for this same reason, makes the turn to one side harder not better. ride it without straps on waves for a while and see where your feet end up...
No set-up is perfect for everything.
3 straps does not really put you on the "outside edge", but yes, on the wave
you want a more weight-forward-on-the-centerline-of-the-board position. On the other hand, for general riding
you want the front foot at an angle to brace against the pull of the kite. If you're in an area that consistently has good waves, a strapless surfboard has a lot to recommend it. However, strapless means giving up the ability to send the kite & JUMP, which I think is a poor trade-off, unless you have good wave conditions. 2 straps is OK for down-the-line, but not very comfortable (IMO) for general riding & jumping.
The other factor is the size
of the board - the smaller dimensions make it more maneuverable & much better for jumping than a bigger, 2-strapped surfboard &, in my experience, you give up almost nothing in low-wind performance - it is, after all, still a pretty big board compared to the average TT.
In the end, I don't really feel this kind of board is a substitute for a full-on surfboard - I feel it's a substitute for a TT. For me, directional riding is just more elegant, efficient, interesting & fun than TT riding.
Hey Flyboy, that's my old board!