You can totally pack the hopper on the Masterbuilt with no problem except that you sometimes have to poke the coals down after a few hours to prevent "bridging". I've used splits on a lot of cooks but generally use wood chunks mixed with charcoal (usually lump) on long cooks like this last one. I started the smoker a little before the brisket went in (4pm) and topped off the hopper when I went to bed around 11pm. About 7 hours in, it was about half burned. In the morning, I topped it up again and it burned to the finish with about a half hopper left. Unfortunately, I forgot to put in the slides so that got wasted. Normally, when you're done with your cook, you put in the little metal slides and it shuts down the coals so they can be used on the next cook. Those are the coals I generally use to start the next cook.
It's funny. If you look up reviews, you'll see all kinds of problems. With having one for over 3 years, I can see that most of the issues are user error. I've had a couple issues only to figure out it was me. If you end up getting one, I can probably guide you through most issues if you have any.
I've had several types of smokers. I really like how this one works. I've always been big on the simple Weber kettles. Now my poor kettle is resigned to burning off internal parts to my MB and storing my charcoal chimney.