There are two versions of the LEM made by HK. The standard one, and the lighter one, for lack of better names. I think the only difference is the trigger return/ pivot spring weight. The lighter one is supposed to be more similar to the Glock, but I can't vouch for this since I've never shot a Glock.
I can tell you, however, that the HK triggers are much "different" than the Sig triggers as well. TO ME, they are crisper, with less stacking. I never could get used to the "spongy" feel of a SIG trigger. Guess it's what you're used to.
Match triggers (which are standard on Tactical, Expert, and Elite models) allow you to adjust the trigger stop for quicker reset and follow on shots.
Look closely on my USP9 Expert behind the trigger and you can see an adjustable screw sticking out - thats the overtravel screw on a match trigger. This trigger is, IMHO, much lighter, crisper, less creep, and quicker reset than the regular USP trigger. Not sure I'd want this on a carry gun either.
I carry a P7, so you've got a 12 pound "cocker" you've got to squeeze, and the trigger must be pulled (not necessarily in that order), before the gun will fire. The safest "carry" system around - again, my opinion only.
As far as 45s go, I can't think of a better all around gun made right now than the HK45. Ergonomics, comfort, felt recoil, accuracy, and reliability are all TOP NOTCH with this gun. Unfortunately, it is only available in Variant 1 (SA/DA) with dococker/safety. I'm looking for another right now just to have a spare.
Good luck with your choice and happy shooting!