Coupla things...
To understand preference for and/or prejudice against fives - in Nashville at least - you have to understand the (at least) two schools of thought. And, of course, there are exceptions to every rule.
The first fives we started seeing here in Nashville (late 80s) were Steinbergers. EMG HB pickups, and REAL narrow string spacing. They sounded extremely pop. That didn't work for many of the producers or artists at the time, but for some, who were trying to sound more pop, it did. At the time, there were the neo-trad artists, like Randy Travis, Ricky Skaggs, etc., who were HUGE. And they wanted vintage sounds. Fives had been making inroads into pop music, largely because with CDs becoming more common and stereo equipment improving, pop producers and artists were recording things with lower notes. Broader range.
So the five was symbolic of a pop SENSIBILITY. Sure, you could get the desired sounds on a five (some fives, anyway), but a five made a statement; "I'm into the pop stuff where all the extended range, big-pillow sounds are happening." It said something about your musical leanings as a player. There were lots of people coming to Nashville at the time from Berklee, Miami, and other schools, and most of them got here not understanding how to keep it simple and play in a real country pocket. The prejudice - when I first saw it - grew out of a nervousness about five-string players being popsters first, sometimes even holding the trad stuff in low regard even as they took the gigs and cashed the paychecks.
Slowly, this began to change. You started seeing session guys with fives. And the music changed. Note that country is only a portion of what's recorded here. Most Praise & Worship was recorded here at the time, a ton of Contemporary Christian, and lots of rock & roll (going all the way back to Buddy Holly, who cut more than half of his stuff at the Quonset Hut on 16th). So guys who were doing a lot of different kinds of work started getting fives, as those other styles were using lower, pillow-ey sounds as well.
In the 90s, artists started cutting stuff that sounded even more pop. The jump-the-shark moment was Shania Twain's "Woman In Me" CD. Huge, almost orchestral range. With its success, everyone started clamoring to get in on the payday, and cut pop-ish stuff. Fives ruled. At that time, if you DIDN'T walk in with a five, they assumed you didn't get what they were doing.
All that has evolved into two schools of thought in mainstream country and an offshoot (Americana) that, with any luck, will overcome them both in time. You have the more pop oriented acts (Rascal Flatts, Carrie Underwood, etc.), and the backlash/trad/"country" stuff (Blake Shelton, Josh Turner, etc.). In truth, fives and fours are largely interchangeable (allowing for range) within those camps, but there is still a knee-jerk reaction in some quarters to being seen as "going pop," and a five is sometimes symbolic of that in some people's minds.
All that said, I would never walk into a studio here without a Fender four. For one, I know I can get a sound that works on almost any tune with it. As for symbolism, it does say to everyone there that I get the basics, and whatever I do on top of that is probably going to be accepted.
BTW, Kevin Grantt (yes, two "t"s), shown in a post above with his Sadowsky 5JJ, plays most of Brad Paisley's tracks with early 60s Fender Jazz basses. I've been at the sessions. Kevin's cartage company shows up with two coffins, containing eight or nine basses, and on those records he mostly chooses one of his (many) older Jazz basses. I've seen him cut with Josh Turner as well, and he used his well-worn Music Man 5 on a couple tracks, the Sad. 5 on another, and an early Jazz on the rest. The five in the picture in this thread was stolen from Kevin several years ago, and through a really tangled turn of events, he got it back about three years ago. He loves the bass for lots of reasons, but it's not his most-frequently-used bass in the studio by a long shot.
Michael Rhodes has come up here as well. Michael's a good friend. I bought his first Sadowsky five (maple FB, JJ, VTC) from him a few years ago. Like most session heavies, he has a LOT of basses. Think 30 or so. In the last 3 or 4 years, his go-to bass for MOST things is a Sadowsky RW PJ5. But he grew into that being his everyday bass. He also uses 4s a lot, almost always Sadowsky these days. I saw him on an Oz Noy set last year; started out with an early (EARLY) Fender Jazz, nearly threw it into a stand after the first tune, and went to one of his Sadowsky 4 JJs for the rest of the set.
Happened upon Brignardello at two sessions and one live gig in the last year. Both sessions: tracking with a Sadowsky 4 JJ. In the rack, a Fender Jazz, Fender P, and a five of some kind. Live gig (Grooveyard with John Cowan): All Sadowsky 4JJ, all night.
Dave Roe was the first to turn me onto the lowered-tuning thing. Lots of guys ARE using it here, often with heavy-gauge flats. I've tuned one bass down and will try it for the first time on a session next week. It really does bring a whole new, broader thing to the track, from what I've heard. Hope some of that's interesting.