I'll throw my two cents in, having owned both boats (and now own a similar pair, in terms of categories). You're moving up from one class to the next; the 'stable' skis to the high performance skis (HPS), so there will be a learning curve. This will be much more pronounced in any kind of conditions, particularly beam chop.
Stability: Expect to swim some, probably not at all on flat water, but you will become 'intent' quickly when things pick up a bit. Bucket time...bucket time...bucket time... In the stable skis, you can paddle them every one in a while and you'll be none the worse for wear. not so in the HPS-you really need to spend 3-4 days a week in them min. to get comfortable.
Comfort: Both are comfortable. IMO the V10/L buckets are amongst the most comfortable out there-their ergonomics are dialed also, and they're easy to remount with the low side rails.
Speed; On flat water, the V10/L will literally walk away-you'll be amazed at the glide. they are fast boats. In the rough, don't be surprised if you're faster in the XT, at least initially. stability before speed-you're only as quick as you are efficient in putting the power down.
Weight: Apples to apples-depends what you're comparing in terms of layup. If you're looking at the Ultra layups, then they will be uber light weight, but you may find them to be a bit twitchy in the rough.
Currently own a Huki S1-R and a Custom Kayaks Synergy-both great boats. the Huki is my 'chicken boat' and a fun friend when things get big. The Synergy, although amongst the most stable of the HPS, is still a leap up from the R. Ultimately, having one boat from each category is optimum, but if you're committed to moving up, the Epics might be a bit more initially user friendly compared to some of the others out there. Certainly, the Synergy is. Good luck!
"Nice? It's the only thing," said the Water Rat, solemnly, as he leaned forward for his stroke. "Believe me, my young friend, there is nothing -- absolutely nothing -- half so much worth doing as simply messing about in boats."
'The Wind in the Willows'~Kenneth Grahame