I wouldn't hesitate getting the MR Visa especially with the sign up bonus above.

It seems to me that in the OP you asked our advice as to whether or not to use a hotel earning c card or an airline one. (Unless there is an airline bonus)I have done far better at redeeming my hotel points than in getting free airline tickets. I have saved a fortune on many very expensive hotels - that's the only time I redeem. I think free hotel rooms are far easier to get than free flights.

So, I concentrate my spending on the Starwood AMX and the MR Visa. I use my airline c cards only when there is a bonus involved.