You start a tad later, with ANY windfoil, compared to a kitefoil, correct, but still possible to foil around 9 knots with the right gear.
But the advantage, which I assume is what the OP seek, is you can ride in almost zero wind, non planing/foiling, and not the same risks of downing the kite so even offshore winds are not much of an issue like it is with a kite.
Going distances with changing weather, lulls or maybe zero wind on occasion - the windfoil wins big time, as you can still stand on the board and pump if no wind, or you can sit and wait for wind.
NOT possible with a kite either (in light wind...)
Having said that, indeed windfoil IS big and bulky, compared, so I stopped windfoiling again because of that.