Like Sarge says practice is everything.
I'm a fan of the 1911. I've always felt comfortable with it.
Not knowing your firearms background: be advised, as a single action semi-automatic it takes a little more care and thought in it's deployment than the double-action mode of the other two pistols you mentioned do (by the way, they are both well thought of weapons). You'll have to decide what condition to have it in for use; ie. cocked & locked, hammer down or chamber empty.
To me "cocked and locked" is the way to go, but some people are uncomfortable carrying a cocked pistol. If you do so, I recommend a holster who's keeper fits between the hammer and receiver. I've never liked "hammer down"; you have to lower the hammer on a live round and the firing pin was resting on the primer in older pistols (pre series 80 Colts/clones), without a firing pin block. "Chamber empty" is by far safest but as imagined slowest and loudest to deploy.
The double action pistols both have decockers (safely lowers the hammer) and block the firing pin. To carry and fire the first round double action, they are much like a revolver, in that you simply need to pull the trigger through it's arc. I believe the HK has several modes of operation available (sa, da, dao) but it seems pretty large. I've only handled one not fired it. I like the SIG 9mms. The ones I have handled and shot were outstanding. I see no reason their 45 would be any different.
Regards,
Greg