Actually I would sugguest that when you switch you learn on a 4 String Bass first. For me, a 5 String is already quite confusing. I dunno how a 6 string would turn out. You can borrow a 4 string from someone or just get a second hand one for under $200.
Recently took up bass as well. In general, it's not too difficult, depending on the genre. If you're doing emo, then it's pick and hammer. More challenging are the jaco pastorius, jamiroquai type songs. One featuring really fast finger picking, and the other some pretty interesting slapping. I found that the thing that was the most alien for me, was the rhythms. For slaps and pops, theres a certain bit of paradiddling to give some variation to triplets and sixteenth notes. That's when it really gets interesting.
A 6 string is an interesting place to start, but it's going to get really heavy very fast. Would recommend probably a 5 string instead. The top 5th string is a low B, so it's just like a guitar without the 1st and 2nd strings, and an extra low B.
woah, its almost 1.5yrs old in between the original post and the latest reply
anyway, just thought that why would some ppl want to have so much strings on the bass when all that is done is playing root notes on it. A down tuned bass with thicker string gauge can do that too(minus the clarity and tightness of course, when compared to a decent 5 string bass)
Imho, if switching from guitar to bass, start with a 4 string bass, get the basics right and go from there. End of the day, got to realised that a bass is not meant to be played like a guitar and there are more than just playing root notes.....
Hearing what victor wooten, jaco, flea etc can do on a 4 string bass, it make me look at 4 strings in a different way. Less is more perhaps