Just my 2 cents..
I have both the Finrir and a Saroo.
I think the Fenrir is great - It is 100% (or nearly) compatible with all the games. It has a nice UI. The only real down side is that you have to open up your Saturn to install it. If you want to play games that need to expansion cart (1/4 MB) then you also need one of those (SaturnKai).
The Saroo works well. I don't know the exact compatibility percentage, but it is up there and climbing. The loading is faster than the Fenrir. The downside, for me, is the menu. It is functional, but if they could copy the Fenrir menu or do one better, I'd really love it. Besides the loading speed, the major advantage that the Saroo has is (in addition to also emulating/taking the place of the expansion cartridge) that it acts as memory cartridge as well. As far as I know, that means virtually unlimited saves wthout having to worry about clearing space of the Saturns internal storage (and you can back it up off the SD card). This, to me, this is the game changer.
Since I have booth, if there is a game that the Saroo can't play, I can always fallback to the Fenrir. Although, I haven't tried anything that the Saroo hasn't played. Admittedly, I've only had the Saroo for a couple of weeks and only played about 10 different games. So, YMMV.
I think the fenrir is very cool, looks good (menu) and just works. The Sarro with it's unlimited saves and speed will probably be my go-to for now on. If I didn't already have a fenrir or a saroo, I'd get a saroo.
Cheers!