In my experience, as I'm just now finishing up a marauder, is that Juggernauts tend to live a little longer compared to marauder in exchange to slower/less dps at lower levels. They can get the job done, but it'll feel a bit heavy.
Marauders, specifically carnage marauders, tend to put out more damage while leveling, but sometimes require a defensive cooldown to stay at a healthy health level, but don't let that discourage you, they have plenty of damage reduction cooldowns.
The general gist of it is: Juggernaut lasts longer in a fight mitigation-wise, marauders can melt an enemy faster.
I say if you want to level a marauder, go for it. They incredibly fun and fast paced (again, at a carnage viewpoint).
Juggernauts are fun too, as I have both.