For me it isn't a pace thing. I like punk, grind, crust, and d-beat after all. It's that so many of them rely on techniques that can create for a fun energetic live show, but don't necessarily come across as exciting on album. Having never seen Parkway Drive, and knowing I hate how they sound on album, I'd bet good money they're fun live just for the pits those slammy breakdowns would create. Whereas on album I think I prefer metalcore bands that aren't just metalcore and incorporate other styles of music, or even bands that aren't metalcore but incorporate the occasional chug in an interesting way.
For me D.E.P. is one of those exceptions as they're not just a metalcore band. They're also extremely technical and sometimes border on being a progressive metal band. BTBAM is more of a progressive metal band that dabbles in metalcore and that works for me. Gojira, Hacride, Klone, Protest The Hero, Botch, What's He Building In There?, and Trepalium are also all solid bands to find those compelling elements of metalcore without being confined to a strictly metalcore shell - mostly because they're more like tech bands with the occasional metalcore moment or song.