One important distinction is that while Shiny Festa's 3D models were pre-rendered, it might not be so for this 'game'. This is a completely different engine from any flagship iMAS game, as can be seen from the background blur at 5 seconds in. This could hint at what iMAS 3 might try to accomplish with its engine, or it could just solely be for this title.
The possibility of it still being pre-rendered is still there though. You never know.
It probably is pre-rendered considering that those character models look slightly more touched-up than the regular models, which I'm pretty sure a smartphone can't handle doing real-time (Unless it can. not very savvy on smartphone technology). I think the best way to note this is comparing the models from that trailer to the ones from the G4U games.
I would not mind in the slightest if this is a sneak preview of how the visuals are gonna look for future games.
Yeah, missed the YT link in the OP.
And yes, it already has more polish than SIF (which isn't hard, because you could easily mistake it for an amateur Flash game), but I'm still highly sceptical. Looks like it's designed for phones, unlike LL which looked more like it was designed for tablets because of the amount and placing of the inputs.
Now that you mention it, that's a good point. LLSIF's buttons are more spread-out which is great for a tablet, but forces you to stretch your fingers out when on a phone. Likewise, this looks perfect to play on a smartphone, but on a tablet, you really have to squish them together.
Maybe they'll have an option like spreading out the inputs so that you can customize it according to your device and see what setup is most comfortable.