Wake boards are made for being pulled behind a boat ski, cable, winch.... ect ect. They have 2.5-3" of rocker and are far stiffer than a flat flexi kite board. If you are really going to spend some time behind motorized pulls then just buy a cheap wakeboard. It will out perform every kite board out there behind a kite.
Friend might have been going to fast all so. Speed should be about 25mph.
25mph behind a boat? That's crazy fast, especially for a beginner! I'm an advanced wakeboarder and prefer it locked in at about 22 if it's glass, and 20 or so if it's choppy. Beginners would have a smaller wake and shorter rope, and should be towed at about 18-20mph. Wakeboards, even with a lot of rocker and big fins, get pretty squirrely at 25mph. I realize that some of the top pros ride 25-27mph with 85' ropes, but us mortals can't handle that stuff.
Re: water starts behind a waverunner....It is MUCH harder than behind a kite, boat, or cable. Waverunners just don't have the low end that a boat does, and then they don't have the lift angle that kites and cables do. The tow rope is almost down at water level, which means it's pulling you straight through the water rather than up and out of it. Imagine trying to water start with a kite unhooked and taking the kite from the edge of the window @ 3 o'clock and then running it just off the surface of the water directly down wind. It puts a ton of stress on your arms/hands compared to all other kinds of riding, and the most common outcome for beginners is for the rope to pull you over your board before it can get planing.