I am right handed, but my preference is a Variant # 4, stainless slide with match trigger and Fibre Optic sights. I use the mags with the extended base plate, as it acts as a bumper pad/ to assist with seating the mag.
The Variant # 4 (a DA/SA--decocker only), lever is located on the right hand side of the pistol, and it decocks the pistol from SA to DA only,...it does not act as an external safety. I did this as it gets the lever out of my way. If I had the lever on the left side, my thumb would be resting on it, and may accidentally press it down, which would decock the pistol. H&K is getting away from this design of a lever on duty type pistols (except for the HK45), and for the new P30, and P30L, the DA/SA pistols have no external safety, only the decocking button now located at the rear of the frame, next to the hammer. Of course they also have the P2000 and its variants, as well as the P30 variants and USP variants available with the DAO L.E.M., basically a light DA similiar to the PARA LDA trigger. I have seen a USP Expert (long slide) in .40 with the LEM trigger reduced down to 3.5lbs!!