Rump roast IMO also makes a good pot roast. You may or may not get a bit more usable meat than with the chuck. You might get a bit better flavor with the chuck, but if the rump is good quality meat it ought to taste fine. Throw a bay leaf in the pot (unless, of course, you don’t like bay leaf.)
Whether the Angus is worth the extra price probably depends on your taste buds. There’s some flavor difference between breeds; not everyone notices it, and not everyone prefers the same one. If you’ve got the freezer space, get one of each and find out for yourself.
Flavor’s also affected by diet and excercise. I’m going to guess that all of your options are feedlot beef; so you’ll be running near the bottom there (though not as close to the bottom as really bad pasture. Good pasture raised ought to have better flavor, though.)
Either will do quite well but you’re better off with the chuck. Rump is far easier to overcook into stringy nastiness while chuck is just about bulletproof with low, moist heat.
I use chuck, I cut out the biggest wad of fat, though. It’s fatty enough in the ‘lean’ part. A can of gravy, some red wine, some water, a bay leaf, pepper, a dash of A-1, a pinch of rosemary, maybe some onion or garlic, and the house smells divine. I have a de-fatter measuring cup somewhere that I pour the finished juice in, to get rid of an inch of melted tallow.
Unlike everybody else, I do not like fatty meat, regardless of the flavor argument. I buy a lean roast and then trim off as much fat as I can. My gf will sometimes collect the drippings to make gravy for her serving.
My husband also dislikes fat. I often get round for stew.
Kinda, yes. We joke about that. And we pass a lot of foods back and forth at restaurants. And sometimes I’ll just take the fatty bit that he removed from his meat.
The point of slow cooking is that a lean cut that would otherwise be tough becomes soft. I personally don’t experience the fat as adding much flavor. I do like having a bone that I’ve broiled to brown goodness (and browning the beef too) along with my seasonings for that flavor element.
Chuck roast, Lipton soup mix, can condensed cream of mushroom soup and bay leaf. Recipe is on the Lipton soup mix box and has been used since the early 60’s.