The Android / iOS Stellarmate App is different from the Ekos interface to Kstars, it is a seperate interface and talks to the running kstars on the Stellarmate - there may be a Youtube video out there that demonstrates this. So the User-experience interface is different to Ekos (but pretty much a lot of the same functionality).
Astroberry includes the apps as mentioned here:
www.astroberry.io/ - you may not have used many of them, but they are included. Stellarmate appears to me to be more Kstars/INDI/Ekos centric with some built-in extra features.
If you are only interested in the Live Stacking then I can't comment too much, it is not a feature I have tried out on Stellarmate. I have a mono camera, and really live stacking is only going to be visually nice with a colour camera. So my methodology is to acquire as many images with different filters, and I only really get to see the results of a nights work the next day after I have packed all the kit up again. Where Live Stacking is probably useful (with a colour camera) is to immediately be able to show off the results of your viewing in a social sense with friends - but you wouldn't use a Live Stacked image to send off for processing to mount on a picture frame, as the best quality is obtained through detailed and intricate controlled stacking, rather than an automated process.
I guess the other benefit of Stellarmate is that you have (indirectly) supported one of the developers of Kstars/Ekos/INDI, which might give you a nice, warm, fuzzy feeling.