Quite different skis. I've skied the Experience, demoed the old Dynastar Legend 8000, but am relying on reviews that I've read (quite a few reviews) when it comes to the Mythic Rider.
The Mythic is considered a stable crud buster of some note; more of an 'old school' ski that likes to be driven (as hard as you like); full camber; wider turn radius; won't really do anything until you tell the ski to do it. Great ski if that's your thing. The OP must know that ski a lot better than I do.
The Experience has early rise in tip and tail, is sturdy under foot, softer in tip/tail and has a narrower turning radius. As a result it's designed to hook up more quickly and will turn more sharply. It's a more modern design so it's happy (or even prefers) for the skier to sit neutrally in the middle of the ski and roll it onto edge, whereupon it will hook up and dive into a turn far more quickly than the Mythic would with a similar edging movement.
I like the Experience 88, but then I'm one of those people who sit neutrally and roll onto edge. If you're used to driving a Mythic you might find the tip of the Experience a little soft for the pressure you're providing. I've seen one review where the Experience line is described as feeling like there's a bit of a 'hinge point' in the front of the ski. The material in tip and tail thins out progressively (to reduce swing weight and allow for a bit more flex) in what Rossi calls their Cascade Tip, which might account for that feeling.
Try to demo if you can. Should be fairly easy to find an E88 to demo.
Best of luck.
Edited by sinbad7 - 11/16/15 at 5:55pm