I liked the soft handle, but I found it worked best for me on the right hand (leaving the left free to work the hip dump). Yes, care must be taken during longhose donation and during reel operations, but I didn't find it a big deal. I had tried a hard handle early on but found it too loose/floppy (clearly not an issue with the soft handle).
I've switched back to the hard handle on the left hand on the mandate of my CCR instructor who also gave me the solution to it being floppy (a fingerless glove). I stick with the hard/left configuration in open-circuit for consistency.
In my view, both hard/left/easily switched or soft/right/rarely switched work for most things, it's just a matter of getting used to it. The possible exception that my DPV-capable friends have related to me is that the hard/left is much preferred for that use case.
I need to play around with the soft vs. hard handle to see how I like it. I usually run left hand / hard handle with a corded light and having it on my right hand feels weird (unless of course I'm switching between hands to accomplish a task).
My primary corded light is the HP50 from Dive Rite and I have the handheld conversion kit for it. Next dive I might try it handheld and bring the LX20 with me to try with the soft handle (thank god for drysuit pockets).