Sweet tourney.
Arguments can be made either way about what company has the best HW's. I tend to watch more UFC than the others, just bc the others are usually on Showtime. However I have seen them all fight numerous times, as i've been a fan of MMA since watching the first UFC on PPV years ago.
That being said, both company's have their better fighters, and both have their washed up, on their way out fighters as well.
Strikeforce has: Reem, Fedor, and Werdum as there top guys. UFC has their top guys: Cain, JDS, and Carwin.
Both have their veterans, that could be washed up: i.e. Barnett, Arlovski, Mir, Cro Cop, etc.
Both have unknown/untested/so-so fighter: Rogers, Kharitonov, Lesnar, Big Country, Schaub, etc.
Both company's have great HW divisions. What it boils down to is who you wanna watch fight. It's an objective question with a subjective answer.