i'ved owned two 97's... liked them both but didn't love them, had a 2001 with the 951 and liked it more but only because it hit close to 60.
as stated above a bit under powered for the engine, so the hole shot won't be impressive, but i'm pretty confident that your holeshot on the gsx isn't crazy good either, but this will not be an improvement over the gsx, and if it is, it will be hardly noticable. (just going from personal experience, no charts or anyting)
since you own the gsx, its probably best to compare those two models instead of throwing the x4 into the mix.
pro's vs your gsx, it will carve slightly better, its just a hair longer and a hair more narrow, (i'm going from memory so verify my info with the spec's if you care) .
I believe its capable of higher speed than your gsx, but might not be faster as a stock, but you can make it faster, especially if you start with the right prop, i've never run the concord but thats what i'm told is the best. It should carve better (see below) so if you lean into the turns, you'll love it for high rpm carving. IMO its a much better looking ski... and imo its a better ski if you decide to do even minimal mods.
cons vs your gsx, the storage bin is wide/flat, (ie: sux) vs large and deep with the GSX not sure if you sit higher but it feels like you do, so you'll find it to be a little more tippy, even though it appears to be bottom heavy, its really not, so, it will definitely feel tippy, i've never fallen off a gsx w/o serious goofing around, but I've fallen off the 97 right at the dock because I leaned out too far...and i've been tossed on a hard turn more than once. Even tho it is heavier than the gsx, its not as stable. Both will handle chop well, but IMO the XP will handle chop just a tad better, and you'll be able to make steering adjustments and really dig into turns in rough water well, but you better dig, because if you don't lean in, you'll feel yourself coming off the side. ps.. if your a bigger guy, you'll look like a monkey riding a football on this
hard turns, hard stops, I think this is worth stating, in my limited experience with gsx hulls, they are what i'd call "surprisingly nimble" I was quite satisfied, but with the xp I found that I could really do a harsh digging 180, power out of the turn and then slap it the other way for another quick 180, once you learn to ride it. and there will be a learning curve, (for performance, standing up with lots of leaning and throttle), but once you get the hang of it you'll appreciate its advance from "surprisingly nimble".. to "really digs".
With that said, some people prefer a ski that doesn't dig as hard or require as much effort to ride, you can definitely do maneuvers with the gsx, and they'll only be about 90% of what you can do on the xp, but you won't have to work as hard doing it, you'll rarely get tossed.
The GSX overall, the gsx hull IMO is second only to the x4, and in some respects is better, its a very very nice design.
I think they both hold the same sized tank or roughly so...
EDIT: I questioned this so I checked, the GSX 15 XP 11... thats a big difference. (the 98+ models have the 14 gallon tank)
would I swap a gsx for an xp... hmmm, tough call. but i'd personally say no if all things were equal. I prefer the relative stability of the gsx, i think its pretty dam fast by itself, i like the larger storage bin, and I like the fact that there are less "one off" parts on the ski so if you have mpem problems or hull issues, you'll pay about 30% more at minimum, (although honestly, there are a lot of 97xp's out there... i see them all the friggen time)
however, this might be a better deal if you would consider it to be more reliable than a troublesome gsx. and this is a very good price. I have seen the exact ski always sell for for more, you could definitely could sell your gsx (assuming its clean & running) for a more than your paying especially if your a little patient when selling.
note: beware that your swapping your problems for somebody elses problems, check the new ski carefully and do NOT be afraid to lowball, show up to look at it when its cold and rainy, the next cold front and lowball the crap out of him... its hard to sell a ski in the winter anywhere but florida or hawaii.
if anything is missing, like the front storage bin, beware those hull parts are expensive, just keep it in mind.
ps, i just dug this pic out for the hydroturf thread, you can do some cool stuff with hydroturf... and you can make it nicer with a new seat, (warning, the seat is a major PITA to remove/recover) (really ! you will make create use of the English language during that project)
same ski, but with the blacktip seat installed.