They are both Brahma's, so no real difference there. I don't know what your hens look like, from what I see both Buff and Light. A Light Brahma rooster tends to father chicks that are colored like him. The Buff Brahma's chicks will probably look more like the mothers. Depending in the hen they will each boy have some influence in appearance, but the Light one will have a lot more.
Since you will be hatching chicks you will hatch more males. I assume you plan to eat those. Brahma's feathers are pretty thick. If the amount of meat is very important to you then you can feel them under the feathers to try to determine might have meatier chicks. To me that would not be important enough to worry about, they both should do OK there.
When picking which rooster you want to be the father of the chicks, pick the rooster that is most like how you want the chicks to be.
I assume you mean predator protection. Different people have different opinions on how much that actually is. I believe you are right in that different ones will behave differently when faced with a challenge. Until they are in that situation I don't have any confidence how any one individual will react. In predator attacks my roosters tend to lead the flock to safety once a threat is identified. I've never had a rooster loose any feathers in a predator attack. In two different dog attacks I lost a total of 13 chickens. I have seen a rooster scare off crows that were eating treats I'd tossed out to the flock. Most of them don't even do that much.
One place I find that practically all do help is that if they will come between a possible threat and the flock if they are suspicious of something. If that is a predator they are putting themselves at risk. If I carry a camera down there he will warn them and they all go on alert, and he puts himself between the flock and me. He doesn't trust that camera. If a large snake gets in their area he will give a warning call to alert them and to signal distress, but he doesn't attack. A rooster might attack a hawk, cat, or squirrel, maybe something even bigger, but I find he's more of an early warning system. I know this doesn't help you in your decision, but I would not read too much into their current behavior in this as to how they will react when danger threatens.
When you have two boys in the flock like that, one is dominant. From your description I'm not sure which is. Some things indicate the Light, some the Buff. Probably the Buff.
You don't say how old they are, maturity levels have an influence on flock dynamics. The girls have a part to play in flock dynamics too. Sometimes the rivalry stirs up actions of the boys to include bad behaviors, often the dominant one suppresses certain actions of the more submissive. Dominance can change as they mature. Many hens tend to like the more mature over the less so the less mature may need to get more physical. It sounds like the Buff is still immature enough that the dominant hen is keeping him under control and he has to get physical.
What does all this mean? I think there is a pretty good chance some behaviors will change when one is removed. I don't know how they will change. I also think they are both still relatively immature so behaviors can change when they mature. I personally would not read much into one hiding in the bushes for now.
To me this would be the deciding factor. I don't know what this aggression actually looks like but if I considered him aggressive he would be gone. There is no guarantee that the Light will be any better when he is in charge by himself. It's quite possible that neither one is the right boy for you.
