MP is one of my favorite musicians. He does a lot of stuff that I love, and I think he's come up with some of the coolest parts over the years. But technique has never been the reason why, because it is not a stylistic feature of his playing. Amazing technique and virtuosity are features of Marco's, MM's and Virgil's playing. Similarly, "groove" or "feel" are not reasons why I love MP's music. Groove isn't even a stylistic feature of this genre. When you think of great groove drummers, you don't think of prog metal drummers for a reason. Have you ever heard of a knowledgable drummer/musician with a good ear and exposure to a multitude of genres listen to DT and go "wow man that's an incredible groove Dream Theater laid down." That would never happen.
Feel is very closely related to groove. It's about how you FEEL the beat and whether you play on top of it, behind it or in front of it and it includes articulation, dynamics and volume control. As a quick example, go back to the documentary and listen to how Marco plays the Spirit Carries On. Then go listen to how Derrick Roddy plays it. Those two feel (all puns intended) completely different. I've probably posted on this before at length (in fact, I think I did a long time ago) so I won't belabor it.
My point is that when I think of MP's playing I think about all the great moments on records like Images. A lot of those parts were extremely creative to me. Someone also mentioned arrangement. I totally agree with that. He's a great arranger. But to say that he's technical or can groove really well, or has a feel other than a straight up rock feel, borders on just funny.