It really pretty much depends upon where you fly. For me, One World offers great value and benefits since I am mostly flying West. BA Silver/OW SPH and above provides lounge access domestically within the USA, including AA's Flagship Lounges, and access to MCE seats on AA. This is something one won't get with the other 2 alliances. OW EMD gives you a waiver of the heavy bag charge - something which I used on many occasions. I don't think United or Delta do that for 'non-native' elites.

As to the earning of TPs, I am still figuring it out. However, I found that booking some (same) flights with AY rather than AA, for example, will get me more TPs. It is still a learning process.

It does look that flying to the East will earn little TPs in most cases, and I am not quite sure why given that these partner airlines have a say of what is credited to BAEC members when we fly with them. It is those airlines paying BA when we do. You'd think these partner airlines would want to be attractive for BAEC members.