The Summicron is Mary Ann, if I have to spell it out. Clearly a better choice for almost every reason.
Before your date with Mary-Ann, you ask the Captain "can she bake an apple pie?"
Before the date with Ginger, you ask if there's poison ivy on the island.
MTF has nothing to do with it.
At F/1.4, Summilux gives you an image where you won't get an image from the Summicron. You're comparing something to nothing. With the Summilux, and, in our Gilligan-alogy, the performance difference is equal to the price difference, but merely being able to pay the price does not assure you will be able to extract that potential from the Summilux. Like Ginger, the Summilux is willing to just take your money.