Bulkhead seats are best for knee space although if you are tallish, then there is not much room to stretch out your legs. The exit rows privide no real advantage other than the row in front does not recline into you. The cushions are smaller too.

One version of CRJ has good bulkhead seats 2C and 2D, so I would grab these if they look like bulkhead seats on your flight. Otherwise it's a wash.