That can be tough without actually playing them. I've played a 4-string Jazz bass with a 60's slim C-shape neck on a 7.25" radius since 1966 when I bought my 1965 Jazz. That was stolen in 1976 and it wasn't until 1985 that I found another Jazz bass with that same neck shape, profile, and radius. I've been playing that since 1985. Even a 9.5" radius on a 4-string feels awkward to me because it's not as curved as the 7.25" radius is. So I'm more than a little bit of a neck snob.
When I first started looking at 5-strings back in about 2009 I picked up a Fender Jazz (MIM maybe) in a music store I patronized and tried it out. The neck was wider and flatter, but still pretty slim, but the edges of the neck were uncomfortably sharp and that's not just the fret wire. They didn't have the rolled edges that some basses do. No idea if that's still true, bur was at the time. I found that I really needed to buy a 5-string because the group I was in played 5 or 6 songs a night that needed one and it was time consuming to tune it down and then tune it back up. And of course, the BL never put two of the ones I was drop-tuning for one after the other.
Had a friend from the Eden Forum tell me that I really needed to look at the Rogue basses, which were being made in Korea at the time and selling for about $220. He had 3 different ones from them and highly recommended them. Nobody had them on hand in southwest Virginia at the time so I ordered one expecting to have to send it back if it wasn't as good as he said. When I got it, I was amazed at the fit and finish of it. It looked great, had a 6-bolt neck with tight clearances, and not a drip or dip or scratch anywhere on it. So it passed the visual inspection right off.
I was worried about the playability because it was so much wider than my 4-string and also had a much flatter fingerboard. I'd tried P-bass necks before and they always felt way to chunky for me and this one was wider than a P-bass. Come to find out it has a 12" radius. I started playing it and was surprised that I could play it pretty comfortably. Figured out the reason for that was that, although it was a wide neck with a 12" radius, it was a slim neck. It was under 1" thick not only at the nut but also at the 12th fret.I later played another P-bass that had a wide but slim neck and didn't have any trouble with that either. So for me the thickness of the neck, not the width, was the problem. I started using that at gigs and it was really nice to just pick it up and play, then switch back to my Jazz when I didn't need the 5-string.
Now that bass doesn't sound as good as my Jazz, but darn few things do. It does have a decent sound though and it can be played in either passive or active mode. If you get an active 5-string, be sure it can also play in passive mode...batteries do run out you know...
This 5-string does work in both passive and active modes, but the treble and bass adjustments don't work in passive. It does have two pickups though with a fat-pole bar pickup in the neck position and a MM wide-bar double row fat pole pickup at the bridge. The pickup blend and volume controls work fine in passive mode and I found I can get a sound I like out of it by just adjusting the pickup blend a little bit. So I play it in passive mode instead of active and I don't have to mess with the gain on my amp because my 5-er doesn't have a real hot signal in passive mode. Just one less thing to adjust when I swap back and forth between 4 and 5-string.
By the way, the one I have is a Korean Made Rogue LX405 Pro. It's not the Pro II or Pro III. I believe the Pro II was made in Indonesia. The Pro III is made in China. Quality Control is pretty iffy with the Chinese manufacturing. You can still get some that are superbly done, but your just as likely or more so to get one with drips, dips, scratches, and poor tolerances. I wouldn't blind-order one. However if you go into a Guitar Center or Musician's Friend and can handle them, you may be able to find a really good one and price is still cheap at ~$219.
I'm not sure I'd do that if it was going to be my only bass though. I love my Jazz and play it whenever I don't need a 5-string, but my 5-string is not my choice for playing all the time. Now, if I had a Lee Sklar Signature Dingwall 5-string, I might find that I want to play that a lot more than just on 5-string songs. I was actually offered an Endorser price on one. But even with that price break, being retired and on SS, it will take a crazy amount of gigs to be able to snag one of these.
Here's pic of it. At least I didn't drool over this picture...
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