There is a difference between looking bigger and taking up more space. As it was mentioned, height changes a lot of things. For example whenI worked at the Biotest booth at the (2006?) Olympia Quincy Taylor was MUCH more impressive than Ronnie because he was 6"4" AND had a lot of muscle. Similarly a guy like Hafthor Bjornsson at something like 6"9" with plenty of muscle would look more imposing AT FIRST SIGHT.
When you take a quick glance, height and frame makes a huge first impression. And to be honest, to an untrained eye, someone who isn't into training or bodybuilding, the tall (muscular) guy can still look more impressive even after more careful analysis.
Obviously for someone who is more used to seeing muscle, it's a not contest that even after the quick first impression due to frame and size, the more muscular guy will look bigger.
But also one thing to consider. It's easy to judge muscle size by pictures. But honestly if you put 5-10 IFBB pro bodybuilders in a tank top and mask their face so that you don't know who they are, you will have a hard time telling which one has more muscle when looking at them in a "normal" setting... these guys have so much muscle that it's almost like the brain has no frame of reference and has a hard time judging size accordingly.
But honestly, Brock isn't the best example for your question. He is a big boy but not that big.... every division I football team has at least 20 guys his sizer bigger. And he isn't tell enough to make a huge difference next to Ronnie who isn't exactly short at 5'11".
Now take a huge and solid NFL defensive tackle who is 6'5" and 320 with a lot of muscle despite having some fat, or a top level world strongest man competitor... in a shirt it might be hard to decide because these guys have a REALLY big frame. But without a shirt it's a no contest.