It is probably best on bass seeing as you don't you don't have to deal with Eddie's 3 signature solos.
You do not have to five star every song to complete it (as I first thought) but it would great if you did, because you would get the "316" achievement for 5 starring all Van Halen songs on expert bass, worth 65G.
The only ones you really need to look out for are "Takedown" by Yellow Card, "Loss Of Control" and "Mean Streets" by Van Halen.
These are the ones I had trouble with, on "Loss Of Control" there are parts of the song that go quiet, just make sure that on the second quiet part, you are on roughly 40,000 and you should 5 star. "Takedown" may take some practice to get the strumming pattern right so just practice. "Mean Streets" is a fairly easy song, except for a not hard but confusing part at the end, just practice, I did it on second attempt.
Note: If you have not already got the achievement for completing the career on hard, you will also obtain that if you complete career on expert.