They're both fast-paced high adrenaline games.
I really enjoy the MET package. The music, the layout, the art, and the rules. I love MET for the rules. It's difficult, high-risk shots, but the stacks are achievable on one ball. Bringing S&D right into a multiball (or a multiball stack) is pure awesome, and worth the challenge to set it up. I love how every shot in MET dictates what your next shot should be. So your next shot constantly changes, and against your will when you accidentally hit the wrong shot...or hit a cross target by accident, keeping it very fresh and entertaining. It's just a genius mode. Yet...simple and accessed without a marathon game and lots of time invested. I actually hope the MET rules are updated in a manner which still keeps this aspect of the game.
I enjoy the mode-based play also, and once code is updated on ST I'll give it a go again. I was disappointed by the art and lack of creativity in the design of ST, but the game does shoot and flow well. I just think it shoots and flows a little to similarly to other machines I've owned or own. I love the theme, though, and if I had to guess I'd say that I'll own a ST LE/Pre down the road at some point, so I hope they keep updating and tweaking the code to make it more interesting.