To me they've all been interchangeable (fine..nothing special) except for Commutair. Forget for a second that Commutair flew the good 'ol ERJ145 (probably worse than the CRJ-200), but they were absolutely horrid in keeping a schedule and/or actually flying a scheduled route. Since they left EWR (or at least left any of my flights), I've found the regional carriers to all be fine.

Not sure where you're heading, but anecdotally (me, I'm the one saying this) I've found that the regionals tend to get delayed a bit more often for a variety of reasons. Less equipment, smaller crew availability, and maybe even some preferred treatment for mainline during IRROPS at hubs.