Having stopped playing five string in practice for a few weeks recently I understand this better than I would have before.
Having swapped a couple of times between the two I feel comfortable about both four and five strings, I really only need it to save from drop tuning or from modifying a four to take a drop tuner. I just like the extra string but I easily can do without. There is something almost organic about an instrument with an odd number of strings. I was the same with my 'bikes, favouring triples over twins or fours.
As a relatively unaccomplished player I'd say swapping back and forth has made me feel less compelled to stick with just one instrument. I find I can swap basses with no inconvenience other than a short period of adjustment. It's helping me to learn what works across instruments and I like that because I can weed out little bad habits that I sometimes develop. Where one bass might forgive me that habit, the next one wont. I think it means I carry less baggage as a player so I am more about the music.
One thing I would say is that a five isn't great for double thumbing because there is less space between strings generally.