Beginning with 5 strings.

[JW56789]

I'd forgotten one other thing:

You will go faster in switching over if you learn new music on the five. Or if you have some tunes that are a handful (say in E-flat or D, C, etc.), try them on the five. Also things, say in F where you're backed in that corner at the end of the neck at the nut, open strings etc. Playing these things with your root E-flat, F-sharp, etc. on the B-string puts you up the neck and a little more comfortable spot to play these things from.

I often find that things where I used to use the open E on a four line up very easily across the fingerboard moving that E to the B-string.

 

[Szaladin]

My first non-beginner bass was also my first five-string. So I had a lot of motivation to put the four-strings to the side for a while.

It definitively helped to play the five-string exclusively for a while.

I also had the impression that the slightly wider neck lead to more discipline concerning avoiding the "baseball bat grip". (Not to say that it's bad in general, but you know.)

I often find that things where I used to use the open E on a four line up very easily across the fingerboard moving that E to the B-string.

Also the sound and attack feel of the E is completely different on the new lowest string. For some of our songs I completely shifted things around. Same notes, but the low G on the 8th fret for example has a totally different punch than the same one on the E-string's 3rd fret.

I'd use the low F on the B-string for fast, punchy things. But on the E-string for clean or reverb'd ringing notes with a whole different mix of overtones.