Boxleitner was good but much more of a traditional TV leading man. O'Hare's acting choices were frequently more offbeat and interesting, and his character had a lot more depth. Sheridan doesn't really change much at all from his first episode to his final appearance.
Seriously, I feel fucking crazy for listing Season 1 as my favourite B5 season but it's true. I love that early mysterious vibe to the show and the cast's chemistry was never better. I know 3 and 4 are the show at its best but I find myself rewatching 1 a lot more. It's the season with the most atmosphere. And it has the best damn opening title sequence I've ever seen. The Season 2 version is shit in comparison.
"It can be a dangerous place..."
*Sinclair turns the corner with a gun as BADASS music kicks in*