Handling a gun only goes so far but the one factor that is important is the feel.
One thing that was universal for me, no matter the make or model of HK, I loved the feel of them. Wanted one but settled for a Sig due to price.
So, the grip handling and how the controls feel for you are relevant.
You can get sight picture feel as well (HK has good sights).
After that its shooting and there is no substitute for that.
It depends on how picky you are or not and thats not meant negatively. Some people are very sensitive to how a gun feels and how they shoot it, some are not or so used to working with their hands and tools that its a lifetime of adapting to the tool vs a more modern situation where tools are being more ergonomic and fit the user better.
I am not. I can tell the difference and have a preference, but I can shoot anything at least decently (we won't talk about the eyes and sight picture!).
I don't shoot the HK any better than the Sig but I do like to shoot it better (not the least unhappy with the Sig, a bit like getting to drive a sportier care vs the Passat.).