well, it is moderately difficult to start playing an instrument for the first time, but it's better to start on something easier like the piano to get a feel for reading notes and rhythms. i play the acoustic/classical and electric guitar, and it has loads of variety, you can play rock, jazz, blues, classical, bossa nova etc., but i dont think that the bass has much variety. i started the guitar recently after playing the piano for about 8 years (still play now, studying grade 6 now), and i found it really easy to start because i knew all the chords etc. etc. choose what you want to go, go with what you think is good, it's your choice.
personally, i'd love to play the ukulele. it's a really cool instrument to have because you can take it with you and stuff, and you can play really fun tunes on it. very cheap too, compared to the electric guitar and bass.
if you are getting one of those two you wanted, then buy a decent guitar, not some cheap guitar, because cheap guitars and basses need constant maintenance, and are a bad value for money. i personally like the acoustic guitar better, because it is better for genres of music. you can basically play a whole range of music, from guns n roses to bj thomas. they are a lot cheaper than electric guitars, and when you think you are ready, you can buy an electric guitar.
a really good site (includes pictures and reviews) to buy any musical instrument, from electric guitars to double bassoons:
http://www.musiciansfriend.com/
you can buy musical instruments from there, but i don't because i live far away from america.
