Well, I've never been a great guitar player nor am i now a great bass player. But i really enjoy playing the bass. I do still go back to my guitar and fiddle around occasionally.
I'll try to answer sub's questions as according to my own experience.
1) why?
For me, I love holding down the groove with the drummer. I really enjoy being the one to lay down the foundation for the song and being the backbone. I also like filling in a little here and there, not that i'm great at it. Plus I also had some training as a drummer, still play the drums. That may account for my interest in the rhythm section of the band.
Also, its up to your own personal preference, cos guitarists naturally get more of the lime light and people (musicians and non) generally notice their playing more. again this is general and just my 2 cents. In a wierd way, I like being the unnoticed member in the band, where if i play it right, everyone enjoys the song. In general bassists know that they'll get little praise from other ppl 'cept other bassists, but I do it anyway cos i love to groove. :wink:
In anycase sub, are you talking about a complete switch where you don't play guitar anymore? just wondering
2)Any difficulties?
Bass playing and guitar playing to me are like worlds apart, I don't really use a pick during playing so its mainly fingerstyle. when i first started, i was really suprised that even keeping a steady bass line was not that easy, as one had to control the tone by the way the strings are plucked. Bassists always say that the tone is in the fingers, unless you really play the bass, i don't think ppl will understand that statement. Even now i'm still trying to maintain the tone and consistency that i want.
I also have rather small hands so it took me a while to get my left hand up to par, especially my pinky, to try to get it strong enough. also, since you play fingerstyle, a lot of other muscles are used on the right hand, Once for me during a really long practice session, my right hand started cramping up. Obviously bass strings are thicker so it presents a different problem. theres also the need to address what neck you prefer, a jazz or p bass style neck or a thick baseball bat neck, string spacing is also another, not to mention 4,5 or 6 strings. although bass and guitar are similar, I sincerely feel they are 2 different beasts altogether.
This is just my opinions and i do hope that they help you sub. I'll be happy to try to answer some more specific questions. good luck.