I finally killed an XL brown bear and am weighing whether to life-size it. My house is currently slam full of taxidermy, but I will be retiring in a year or so and will have plenty of room in a new house. A buddy suggested that if I'm going to wait to have it life-sized, I should get it "show" tanned rather than a regular tan. I have no idea what the diff is, but it is likely that I will have it tanned and not get it mounted for a year or two. What do the experts have to say about this???

I've never heard of show tan

Well first off, never heard the term SHOW TAN?
You have wet tan and dry tan.
BOTH cane mounted anytime.
Get it dry tanned as the tannery does all the grooming and no oils will remain on the hair only in the leather skin of the tanned bear.
In getting it dry tanned you loose some time that it can be mounted..
Get it dry tanned and within a year soak it up in water let drip dry for an hours, roll it up in a bag and freeze it. You can see that skin frozen for 10-20 years and mount it anytime.
Leaving a dry tan sitting there over a year un rehydrated and left out to SHOW, I guess that what he's talking about, it can have to much acid in the skin and break down the fibers so that when you got to soak it to rehydrate it is could fall apart and be unmountable....
Get it wet tanned and juts freeze it. more involved when mounting as it will have to be washed to remove oils from the hair...