In short, you have the "Pancake/Whiff" guy, who will drive back but not maintain.
Or the "Engaged/Skates" guy, who won't let the guy go but will be 20 Yards behind your LOS.
Depends on your Offense which is preferable once you get to these types. Staying Engaged SEEMS the most valuable, but you might only need a 1/2 Second of 'Popping Pads'... like you do Outside Runs and your Strong/Bad Blocker is a G or C... he only needs to 'Pop' and drive back so the RB can blaze to the edge, because that DT/ILB isn't going to catch the RB AS LONG as the OL got his shot off. (It's the Wiff that will kill you, sucks when an Outside Run is blown up on the INSIDE.)
On the other hand, if you Pass a lot or do Inside Runs, a guy on Skates creates holes for Defenders to flood through and attack your Back Field. So he's got his guy locked up, but he's opening a flood gate to your Football.