PMUA always blocked seats A and D in rows 3 and 4 for weight and balance (window seats in 3 and 4) on the CRJ200. They were almost better than the exit row.
Two CRJ200 flights this week and I noticed that those seats are not blocked on the new United. At least I didn't lose my exit row seats in the system integration.
IMHO, nothing is ever better than the exit row isle seat on this plane. YNMV.