They are each quality handguns......
so, you need to pick one that 'feels' right for you hand, rent it and shoot them all...if possible.
Then makes your choice and pays your money. Get a good IWB and belt, buy a lot of ammo and learn it well.
Of the three, I like the SIG 245 best. Cause it fits me and I like the size. The Glock 36 would be next on my list, mainly because of size...though I'd have to have the grip redone for a better fit. Athe HK is nice, reliable, accurate, but not small enough for my Concealment tastes. But each has their own set of parameters to decide and choices to make. Whichever fis the hand and the wallet best.
You have narrowed it to three excellant ones in a proven cartridge...so you really cannot go wrong with any of them.
Jercamp45