I have many of each and quite honestly like each equally for different reasons. I use my HK45 on Duty and use my HK45c as a back up on Duty and as my primary CCW while off duty.
The HK45 I prefer to carry with a 5/6 detent so that I can carry it cocked and locked, single action and ride the thumb safety as I initially viewed the platform as an improvement to my beloved 1911 and a crossover of sorts, between the 1911 and the Glocks I had carried the majority of my career. However I would probably enjoy the pistol just as much with a LEM and to be honest is probably the variant that has the most merit. Great trigger for a polymer pistol, bomb proof, great ergos and shoots one ragged hole.
The HK45C I believe is more applicable to most end users. It is a bit of a jack of all trades gun. It has the natural footprint of a G19. I think the ergos are still excellent. I put talons on mine. You can run the pistol with elephant foot mags as more of a full size pistol config or you can run flat plates as more of a compact. I do not like having a thumb safety on these and wouldn't carry one without it being converted to LEM. LEM is a great trigger and also further minimizes the footprint of the platform with a bobbed hammer and removal of the safety. Again, bombproof, great trigger, great ergos and shoots one ragged hole.
My HK45C gets double the carry time my HK45 gets, but I shoot the Compact the least. I slightly favor the HK45 compared to the HK45C. I shoot them both very well with a slight edge going to the HK45. The only thing I preference is putting a 10-8 front and rear on both platforms.
In the end, I wouldn't want to live without either. I know that in the world of HK pistols it seems that people are either HK45 or USP 45 dominant. As recently picking up a USP 45 I can see why. But while I've no intention of ridding myself of my USP and will be adding more USP's to the stable, I still preference the HK45's to the USP. Both however are equally awesome in their own ways. Buy, buy, buy..... You only die once.