I would say stick with the 5 string,just for the simple fact you never know when you might go up on the neck to the B.
I rarely use my fifth string (hardly ever in cover songs),but whenever we do an original,my hand always seems to go to the B string,even if it's just for a groove or two.
But take this into consideration:
I didn't even originaly by the primary bass I use because it was a 5 string,I just liked the tones it had,and it played very,very,easy in my hands.
My suggestion would be to not even worry about how many strings the bass you're looking at buying has.
If you like the way it feels and plays,that should be what matters most.
Whether it has 4,5,6, or even more strings than that,in my opinion, should be secondary to the sound and feel of the instrument.
On the flip side,it woudn't hurt to have a 4 string just to get used to how different it feels to not have an extra string.
I own 2 5 strings and 2 four strings and the string difference doesn't bother me anymore,but when I first started playing a five string it really threw me off.
The fat B seemed to really confuse me when playing.I would lose posistion easy,and not know were I was on the fretboard.
After a while I finaly got past this,and it no longer bothers me.
I say just get a bass that feels comfertable and plays good though.