The misi is on par with the lrbaggs but it is $50 cheaper, and does not need batteries.
For those reading this thread, be careful with "on par". Price and features aside (some will call a capacitor a feature - MiSi certainly does), these are two very different pickups. Yes, they may share the same undersaddle, but the preamp is different, and this, IMO/IME is the crux of the decision. Some players actually like the Fishman quack, and I've heard of one artist in particular that uninstalled a Baggs Element for a Fishman Matrix (the MiSi pre is very Fishmany). I've also heard of another artist who wanted the Element specifically, and NOT the Five.0 in an `ukulele.
Note: the install of the Baggs is more finicky than say, a Fishman. I'd venture to guess that the MiSi would be similar to the Baggs. While I've not installed a MiSi, I've heard a few of them live. Fishman is a nice, non-eventful install, but it goes in much differently than a Baggs. Your installer will know this. If I had a choice of installs, it would be a Fishman. If I had to play through the instrument, Baggs for sure.
My suggestion - whatever pickup you have installed, get a Baggs ParaAcoustic DI for live sound. My `ukulele player in my group would tell you the same thing. His newest favorite setup: LRBaggs Five.0 into LRBaggs ParaAcoustic DI, XLR into mixer. Disclaimer: I'm an LRBaggs Dealer, so I'm a little biased.
To take away from the Bias, I heard one of Rick's DTar's at NAMM a few years back - awesome awesome pickup, TONS of headroom, no quack, no feedback. I think it was the Timber-Line. And the battery box is mounted in the instrument, with an option to outboard mount with a TRS cable (I may be wrong on this one). I didn't get the 18v benefit of the DTAR, until I converted my bass from 9v to 18v - completely different instrument. Of course the ParaAcoustic increases gain as well, but the DTAR does it by itself.
You've been given recommendations on different pickups, but all of these are blind. We don't know your application, which could help. For all we know, all you want to do is record, and that's why you want a pickup. Then you can pretty much disregard everything I said.
BTW - Aaron at HMS did a pickup shootout, with a few of the pickups mentioned here.