With a five string, you get a 4 string bass plus more. You can play it as a four string using the B string as a thumb rest. And when you want or need really low notes, use that B string.
I think you should consider a five string. Then you would have both a four string and a five string.
unless you play like stanly clark,or victor wooten ,really how often do you need more than 4,i certainly dont play like either,them boys use every one 5 or 6 ,but thats just me peace
One nice thing about a five string is that you can play Drop D songs, and songs in other tunings, without having to retune. (And then tune back to standard tuning. ) And if you do play songs that go lower than E, a five string sounds better than an octave pedal, IMO.
A five string is a four string with one more, lower pitch, string. More versatility. If you already have a four string and are thinking of a second bass, you should consider a five string - unless the music you play never requires anything lower than the E string.
The best thing to do > Go on and try out instruments B4, B5, 74 and 75 on music store. It's only way for you to have a better experience and see which fits best to you. Cort basses are always good!