I enjoy both characters. I think they're very well written and played to perfection. It's really the two main characters, their interactions with each other, and their interactions with others that's the draw of the series for me - the mystery of the week is mostly secondary. And when it comes to JLM perhaps I enjoy him so much on the show because, as I've mentioned before, I've been a fan of his since the first season of his series
Eli Stone back in 2008, and even before he did the DS film I was checking out his other work.
As for not being able to understand JLM as Sherlock, as I've also said, I can honestly say I never have trouble. But I know I'm probably in the minority there because people here have said they have trouble along with a few of my friends in real life who also watch the show. One theory I can give is that over 40 years of watching English imports on PBS must have tuned my ears to all sorts of English accents because I never have trouble understanding any of them.
Well, that and my own English ancestry. Maybe it's also something that's ingrained in my DNA.