I'm rerouting a DONE4 RTW (on AA ticket) which has SEA-LHR and I'm changing it to SFO-JHK-LHR.

There's a choice of AA or BA for the JFK-LHR leg. How do I work out whether AA and BA will be priced the same, or will generate different YR/YQ? Google Flights shows the two as identically priced on a regular one-way ticket: is it going to be the same if it's part of a RTW?

The AA RTW desk isn't able to help because they say they can't see the YR/YQ until they send it to pricing, which requires cancelling my current itinerary and booking AA to get a price, then rebooking for BA to see that price, then rebooking for AA if that's the one I decide on .... Very cumbersome! I wish there was a simple way to see YR/YQ, even if it's an estimate.

Advice welcomed please.