We were on the St. John's River and Lake Monroe this past weekend (near Sanford, FL), and the latter was a little windy. I'd call it light chop. The ride was comfortable at 30 mph. Keep in mind these jet boats do not have as deep of V hulls as stern drive. That means they jump on plane more quickly, you feel the bumps more and they tend to slide around with lateral wind and wakes absent stabilizers like Cobra Jet fins or TVs. That applies to all of them.
I seriously considered a new SX210 and made my own comparison sheet to help decide. They're attractive. Why not? Primarily because +$14K didn't justify the benefits - a little more room (we usually have 2-4 and rarely up to six), extra/redundant engine, better chop handling (+800 lb boat), and tandem trailer is safer from a blowout standpoint. The negatives were: 1,100 lb more to tow, double the gas usage, and more difficult to get in and out of my driveway. TowBoat US service is included with my GEICO insurance. If that single engine unexpectedly dies on the water, I'll anchor and call on the cell or portable VHF for a tow. That's an acceptable alternative to paying once (purchase price) and recurring basis (gas and 2x maintenance costs) for an extra engine. Those two models of boat have almost the same top speed.
If more choppy water was the norm, we had more people going, and/or regularly went out into the ocean vs. sticking to inland lakes and intracoastals, I would have opted for the 210 and paid to store it somewhere. I'll revisit if needs change. For now the SX190 is almost perfect. You'd probably like the 21 footer. If money and convenience (storage) were no object, I might well have just grabbed one. Matter of priorities.