I have a friend that was on the -145 at Beagle and then went to Skywest and now obviously fly's the CRJ.
I asked him this same question one day, and basically laid it out like this:
CRJ-200 < EMB-145 < CRJ-700
The CRJ-200 is a piece. The EMB-145 has fantastic systems for the most part, that work for the most part, and it's an easy aircraft to fly. Personally I can't get used to the rams horn crap, but some guys love it. I'm in the minority of guys that don't like it.
The CRJ-700 has a real yoke and better descent planning capability. Descents in the EMB-145 are done using mental math, and the FMS isn't any help to you. The CRJ-700 has the banana on the MFD that makes things a little bit easier for ball parking in my opinion, but after flying the EMB-145 I'm always going to end up doing the math in my head no matter what (and you should probably do this too).
Some guys will compare climb rates between RJ's, and it's not really much of a comparison. The CRJ-700 has the best power to weight ratio of out all the RJ's out there, and will out climb the CRJ-200, CRJ-900 and the EMB-145. The CRJ-200 gets bogged down easily, and where the EMB-145 can climb at 1,200 FPM at FL300, it's doing it at Mach .65. The CRJ-200 will climb at 500 FPM at FL300, and does it at Mach .70 or something like that. You're not flying an MD-11 where you can climb at Mach .80 and 6,000 FPM, so you're really splitting hairs in performance land.
The CRJ-700 has leading edge devices, which I would imagine makes speed control a bit easier. That being said, I've never had a problem going down and slowing down in an EMB-145.
The EMB-145 is the loudest jet in the history of mankind. You WILL need an ANR headset (a lot of guys are using the new Bose headset) or something that you can plug your ears up with (Telex 5x5 with a custom earmold, clarity aloft, something like that).
I would personally go where you could get a line the quickest. Nothing else matters in my mind.
Oh and at Beagle, the CRJ-700 trips are bound to be better once you DO get a line, but still if you can get more senior on the -145 quicker, go there.
OH, and the Beagle -145's have that toy FMS. That thing is a piece of crap.