Originally Posted by
gabrielexposito
It's a no brainer for me:
Transfer 50k Amex to BA and book Aer Lingus business class (just 25k each way, best transatlantic deal out there). Buy cheap ticket to Boston and look into tickets to Edinburgh/Glasgow with Aer Lingus OR Ryanair.
From experience, in Boston they will check your bag all the way to EDI/GLA if you're connecting with Aer Lingus. With either Ryanair or Aer Lingus, though, you will most likely have a long connection time in Dublin (annoying to wait, but chance of misconnect is low). However, my business class boarding pass from my previous flight has been enough on three occasions to let me into Aer Lingus' rather comfortable lounge.
Also, why not spend a day in Dublin? Easy city to see in a day, fly out to Edinburgh the next?
OP specified 6/14-17 so although a sidetrip to Dublin sounds good, I'm assuming there's a schedule that must be met. Plus, neither United nor Qantas shows availability on IE for those dates, even in economy, so it's unlikely that a transfer to BA would provide a solution for his particular problem. By the way, OP, should you decide to transfer to BA, Choice, Best Western, or any other program from MR, it's not a bad idea to check for availability first before you lock you MR points into a particular program--once a transfer from MR is made, you can't transfer back.
Business may be a good use of miles, but since the OP has just less than 200K points total across all programs and seems to be on a schedule, economy for 40K out of JFK, one of the airports he's indicated he could fly from, seemed a bit better option than 50K out of Boston for business. Of course, if he could make Boston an option and business seats are available, it's definitely worth the 10K upgrade cost.