Might have a live recording of very poor quality of the Realist and the Full-Circle, but it would take some forensics to figure out which was which, if I could find them at all. I'm a "mic only" in the studio guy. So every proper recording I have is without a pickup (which is why I like the SoundClip option.)
There are differences in sound, but if you're talking about gigging in the types of places that most people gig, there are factors at play bigger than those differences.
The Full Circle sounds the best and is generally the most useful in my experince. If it installed a little bit differently, I might still be using it.
The Realist has a little less clarity, in my experince, it can sound muddy. It also marks the top in a way that I don't appreciate, but it's not the end of the world.
I'm using the SoundClip and I used the Ehrlund for a year for the same reason. I don't want it or anything else on there when I'm not using them. I don't think the SoundClip a better pickup than the Full Circle. It can sound as good, but it takes some attention to get it sounding that way. Not as much as the Ehrlund, which CAN sound better than any of them, but it's not for the faint of heart. You can read about the difficulities with it. And when it sounds bad, it sounds the worst of all.
If you don't care about having a pickup mounted on your bass, which most people don't and I'm not suggesting that you should, then I'd choose between the Realist and the Full Circle and I'd chose based on how you feel about how they mount. Strings, setup, technique will make a bigger difference in tone, as will the amp you're using for that matter.
The only other, practical option are various types of bridge wing mounted pickups. I think some of them have started getting a little bit better, but they all have a similar characteristic that has never resonated with me.
Don't over think it. Realist is a good suggestion, so is the Full Circle.