I have a Blue Sky AMEX card but I don't use it unless during those AMEX promo like ESSO credits. I only keep it as it is my oldest AMEX card that I have.

My comment to your situation will be that use both cards. Since you stated all your redemption will be travel related, hence use the Blue Sky card for all those non-2X MR location. The question you need to ask yourself will be can you get enough MR to cover the annual fee.

i.e. do you spend more than $20,000 on all those 2X AMEX Gold locations.

This is assuming you are using both MR or Blue Sky Points to offset a travel transaction on your statement. You earn 1.25 with Blue Sky while 2X with AMEX Gold, using both points worth $0.01 each (MR "TripFle rewards" at 1000MR for $10 or Blue Sky at 10000 for $100) For each dollar you sent, the differences will be 0.75 point. $150 / 0.75 / 0.01 = $20,000

If you do not charge >= $20,000, then you might want to only use the Blue Sky card.

Hope my explanation is clear.