I've played both guitar and bass. After some frustration with guitar i switched to bass, and i found it great at first it lost it's charm after a while. I want to be a frontman in a band, and my friend picked up the guitar so I'm thinking about picking up guitar again. But for this i'm not sure what's the best option, should stick with bass, play guitar again, or play both.
When I think of a "front man" for a band, I usually think of someone who is a vocalist or guitarist. There are exceptions though.
Someone mentioned Les Claypool (he rules!). How he sings and plays like he does I'll never know!
Sheryl Crow plays guitar and bass, and I definitely consider her a front ma…front person;)
In the realm of bass-playing front men, I'd consider Dusty Hill of ZZ Top a co-front man (along with Billy Gibbons). He's sang on his share of hits.
There's Gene Simmons of Kiss, bass and co-front man along with Paul Stanley. And, I would be a total schmuck if I didn't mention Lemmy from Motorhead!
If I can go waaaayyy back, some other bass playing frontmen:
Peter Cetera of Chicago
Greg Lake (Emerson, Lake, & Palmer)
John Wetton (Asia, King Crimson)
That all being said, I can tell you that being a singing bass player is tougher than being a singing guitarist. Primarily, unless you've got a really good monitor system, you don't have the entire chord to reference your notes from. But, I can tell you, the fact that I can play bass and sing harmony has gotten me a lot of work. I'm not the front man, but I'm taking checks to the bank 
In the end, play what you love and play for the song. And if you want to switch off on some songs, do that!
Greetings from Austin, TX
Ken