Is the Signature Balcony deluxe suite worth the $400.00 upgrade from the one bedroom balcony suite ( MGM web page pricing).
Not sure on your specific question, but you may want to check out sites like VRBO to rent out the Signature. It got over flooded with residences and the owners usually have much better prices than going through MGM direct.
I thought the deluxe suite was a step down from the one bedroom at the signature. When I booked my reservation I was asked if I wanted to upgrade from the deluxe to the one bedroom, not the other way around.
To answer your question - I would not pay additional $400 to upgrade to the one bedroom suite. You didn't say how long you were staying, but for me, it's not worth it. Are you going to be happy in the deluxe if you don't upgrade or will do you really want the one bedroom?
Weird that it is 400 more for you. I booked 4 nights for the one bedroom balcony suite and it was actually $5 cheaper than the deluxe version. This was thru MLife