First Class all the way. I am moderately claustrophobic, which proves interesting when you fly 110-130k miles/year. Regional jets are my favorites precisely because you have the A side of the plane all to yourself. I would suggest a bulkhead (i.e. 1A) so you have no one reclining into your space, PROVIDED the bulkhead doesn't have restricted legroom. Oddly enough, most regional jets have first class bulkhead seats with plenty of legroom, while mainline aircraft can be quite restrictive.

My backup strategies for dealing with this include:
1. Aisle seats. Always. The only exception is if the row in front is missing the window seat, as is the case on many A321 or MD-90 configurations.
2. Use Seatguru and Flyertalk to find the rows with the most legroom. Often exit rows have even more legroom than non-exit seats designated as Economy Plus... but not always.
3. Exit rows somewhat limit the size of the person that can be seated next to you, as seatbelt extenders cannot be used. Even so, exit rows still give you veto over your seatmate, at the cost of being reassigned elsewhere. If you're stuck next to someone who is really in your space and airlines won't enforce their customer-of-size policies, all you need to say is that you don't feel comfortable sitting in the exit row and need to be reseated.
4. Open your air vent. I find warm, stuffy air greatly contributes to feeling trapped.