I went from a '93 SN196 to my '04 LXI about 3 years ago when my kids were 7 and 11. Unfortunately, I can't comment much on the slow wake comparison, as my older one didn't start slalom until we had the LXI. The LXI wake looks pretty big to me in the 20-25mph range, but starts getting pretty reasonable above that. I love the wakes for my rec skiing at 34. I think they're a little better than my '93 SN at that speed. Definitely seems like the wake quality degrades less as the passenger/cargo load goes up.
And, although the OP didn't ask, there's a huge benefit over the 19ft boats in room and versatility. Just the moderate extra width and length, along with ski locker and tower for stowage, makes a huge difference. And, although the OP only asked about the slalom experience for the kids/slow-speed, my younger guy loves surfing and wakeboarding for which the wedge is great. And, who even knows if kids that age are ever really going to want to slalom?
So, it's probably not the right boat if you're just trying to optimize for 20-25 mph slalom speed, but, it's been great for our family of 4 for a whole bunch of other reasons.