If you want a 5 string you should get a 5 string. If you don't want a 5 string, forget about it because you'll never adjust properly. I have friends who didn't want 5 strings but tried them because everyone said they needed one, when in fact they didn't want one, so adjusting to the extra string became difficult. I on the other hand had been playing a 4 string for about a month (i borrowed it) when I bought my first bass. As soon as I walked into the guitar store and played a 5 I knew I would have no trouble.
I thought I wasn't using my B string much lately, but after playing a 4 string again, I decided the 5 was definately for me. The 4 doesn't do it for me anymore. I'm selling my last one on Ebay as we speak!
So my advice is this, try them. If you like it, get it. If you don't, don't listen to what others are telling you to get.
Good bass under 300 bucks:
Peavey Millenium BXP or American if you can find it.
Any peavey really...
thats just to name a few.