My old flock was all Bantams of various types, the sweetest and most gentle had been the Old English games. Best roosters! Many colors too. This time around that was the first pair I got, and so far, they're the only two that LIKE being held and babied, no food required!
2nd to them, Black Bantam (not the black japanese... never had those). Again, way sweet roosters, dainty little hens with very soft voices.
3rd Cochins, great setters! Mine were usually daily layers in peak season. Didn't have a rooster for them, but the hens were great!
BUT, it depends on how they were raised (lot's of holding as chicks or human interaction?) and the temperments of the line, and so on. If these Seabrights were hen raised and only saw humans at feeding time, you'll know how they are when you go see them. If they're caged when you get there... hold them. If they don't like it or don't act calm, you don't want them. They'll be flighty, a rooster is more likely to be mean, and they won't ever want to be a pet.
At fairs I would "test" the roosters, by pointing fingers at them and dropping them down like a rooster head does in a fight. Those that responded back the same way... pass. Those that hid in the corner... pass. Those that looked back at me like I was stupid... buy. I only intentionally buy older roosters, over 5 months old, to test out that personality. The only 3 roosters I ever had to cull for aggression I bought as chicks.
For the 3 years I had Bantams before... the most common breed I came home with were Old English. I'd pass rows and rows of cages, testing out various roosters, and that's been the most reliable breed in terms of friendliest and sane roosters.
I had Seabrights, both silver and golden. The hens were nice, the roosters nice to me and each other, but they fought a lot with my black bantam roosters. The Old English roosters were too busy escorting their hens around to get involved in the "coop drama".
