DFW-HKG on AA metal puts you on one of Discount Dougie's Dense-Pack 777-300ERs. The Y seats, including MCE, on those airplanes are, without a doubt, the smallest and most uncomfortable seats I have ever ridden in a scheduled airliner. (The ONE AND ONLY seat worse than that was on a charter DC-10 hop in 1999.) Yes, PE is worth the extra spend on that hop on that airplane.

HOWEVER, COMMA, look carefully at your options. Talk with a good travel agent, if you have one available. You may be able to do the TPAC hop on JL or CX metal, as opposed to AA metal, in PE, for about the same spend. The difference will be night and day: both JL and CX eat AA alive on hard and soft product.