Yeah, I agree with ya'. I was playing both 4's and 5's, and switching whenever the song called for a real B, then, my choice of basses was determined for me. I switched to 5's out of necessity, my gear got stolen, and I could only afford to replace one bass. That pretty much meant I was going to be playing a 5er. That was years before we formed the band I'm in now, and I've been in this band for 15 years! Same type of schedule, 100+ gigs/yr(plus we've already booked most of next year!), and almost all of that has been on a 5er. I've had a few 4's over the years, but I never really played them. I'm so used to playing 5's, that 4's just feel bizarre. BUT, I just ordered another 4-string, because of my one issue with playing a 5er...
Dropped-D.
99.8% of the time, dropped-D on a 5 is simple. It may require some finger gymnastics(I like to use Slither/Velvet Revolver as an example), but it's very doable. That other .2%, can't really be played any other way(Killing In The Name/RATM)but in Dropped-D, and, to me, Dropped-D sounds better on a 4 than a 5. Sure, you can tune to Dropped-D on a 5, but it just doesn't sound the same and there's that extra string that you're not gonna use...
Still, if I was gonna pick one bass to play "bro country", it would, without a doubt and in no uncertain terms, be a 5er...
Yeah, Killing, Slither, Sound of Madness, etc... I typically play on a drop tuned 4 string - but the ONLY time I play in a drop tuning is when I need to... I don't really like to play that way, since it changes the way I have to think about the instrument - whereas, I've learned to think of a 5er as sort of a "continuation" of a 4 string... I would change over completely to 5s, except I typically only need one for 30-40% of the songs I play - and have some really nice 4 strings I would miss playing... Also, my 5ers are a bit heavier, and not as comfortable to play, neck-wise - I can't "rock them" like I can a 4 string... I'm my most comfortable with a good P Bass, to be honest...