I assume you are referring to a Kona One (K1)? If so you really cannot compare it to a sailable SUP, 2 different animals for 2 different purposes. Sure they cross paths as light wind boards but a K1 is a windsurfer first and other things second. SUPs are SUPs with or without a sail and most are designed for paddling or/and waves.
I have a K1, I noticed an earlier thread about the decline of our sport and the praise of the hey day of one-board one-sail ideology of the late 70s and early '80s. The K1 is the noughties version with the benefits of modern technology. This board might still hold the key to bringing back the masses. Speed isn't everything, getting people back on the water and having fun is!
Since I returned to the sport 1.5 years ago I noticed the attitudes of people with hi-po gear has carried on from the very early '90s when I left the sport. Emphasis on speed still remains but gone is the cruising or navigation around wider open waters. Hey I love planing like everyone else but the longboard offers something different. With the K1 you can cruise in sub 10 knots and pull old-school longboard tricks to add to the entertainment...good fun. It glides well too.
But when the wind creeps up to 15 knots I'm nearly planing with a 7.5 (I'm 100kg), I can't even get my Fanatic Cross 140 planing at that wind speed with the same sail, and the Cross is a short wide mutha and was made famous in its day to plane early!
15-18 knots and the K1 lifts its skirt, I've used it in more but a short board becomes too inviting, hook into the harness line, move back into the straps and the whole board rises out of the water and skims on its tail. Bear away with your sail or by foot steering and you can ride its fin all under perfect control. I have no doubt when planing this board won't loose any speed against a Freeride board. And you can carve gybe the thing too!
As a SUP it's doable but requires a bit more balance as it is only 70cm wide with a very bouyant 220 ltr giving useful float for heavier riders, I haven't done it yet but I have no doubts it will go DTL easily with sail or paddle, but I don't expect it to do any squigglies. It just hasn't got the rocker or rails for it but a talented rider I'm sure will surprise...and that ain't me!
Pointing ability is very good in light air, but even in 10-15 knots I use it without a centreboard and loose very little. If I sailed it in a tidal lake with a light wind and current perhaps I'd use the c'board more often. I just ride it like a giant Freeride board with the c'board removed most of the time and still get home. I can even water start it in as little as 10-12 knots, I hate uphauling coz I'm lazy and let the sail do all the work.
The K1 is for someone who wants a windsurfer first with all the construction benefits of one and other duties second. If I was returning to the sport and looking for the buzz windsurfing offered me before I would not hesitate to get a K1 again. It's a keeper too, I've got a shorter 260 board for higher wind duties so I'm well covered. The K1 makes a good teaching board too. I might get a paddle for it for exercise.
Here's a pic of one jumping. Who says long white boards can't jump.