I have owned and driven both a 2001 X-22 and 2001 SX-22. In my opinion they are stock what they are supposed to be. The X is much nimbler and has a better hole shot. It gets on plane faster, but it is nowhere near as stable. The X can be a rough ride if the wind kicks up a bit. The SX is stable and still has a good hole shot, but it takes longer to get on plane. Turns take longer and you have to have more weight up front to balance her out. When I got my first SX after having the X, I was a bit disappointed in the hole shot, but after putting a 4 blade on it, the hole seemed about the same as the X. Also, the stability factor in the SX is the #1 selling point for my wife, who doesn't like a bumpy ride. No worries in a bit of chop. My wife also prefers the seating configuration and the amount of trunk storage. It is a much better family boat in my opinion. That said, if you ski at all, the X is for you. The wake unballasted is very flat wheras the SX wake is much bigger even unballasted. Not ideal for skiing, but good for beginning boarders. I haven't seen an X with a couple thousand pound on it, but an SX with a few thousand throws a big ol wake. For my family, we far prefer the SX for the type of boating we do and the lakes we ride on. Oh yeah, the X also gets better mileage. The SX is still much better than other boats but we burn more gas in a day with it than we did the X. One final advantage to the X over the SX, it is a cool lookin boat. SX looks tough and cool, but X looks like a manly man's boat. There's my two cents.
