A New 45mm vs. the SMC Pentax-M 1:2 50mm that I already own

I would like to hear from everyone who already owns and uses a 50mm film lens as to how the new 45mm lens compares with the old glass. Just how much better do you think it is IQ wise if you had to give a percentage? I am already assuming that the autofocus would probably work better than my aging eyes. Here is an example of a portrait from today. Messed around with sliders some in Lightroom, but I haven't had much of a chance to work with the program, so not much done.