Unity is nowhere near as powerful as Unreal. Unity is more for indie games than anything else.

We don't know what type of Tegra Nintendo went with though, for all we know they could have gone with the Tegra X2 since a lot of rumors talked about that as well with Nintendo apparently getting a good deal. Either that or a heavily modified Pascal Tegra X1 so it would be more powerful than that video anyway.

I'm hoping they went with the Tegra X2.

It must be TX2 if not i'm scared.

Same. I really hope they went with an X2, if not i'm really worried about the power of this thing. I don't want Nintendo to have another Wii U and make a system that's too underpowered to get third party ports again.

X1 is like over a year old I can't imagine them not at least upgrading it.. Even if it's not quite the x2. I am cautiously optimistic. I was real down on the system but I have watched analysis videos of the Mario game zoomed up and slowed down and it actually looks quite good to me.

Well even if they are using a Tegra X1 what's being said is that they are using a more modern and upgraded Pascal Tegra so that alone would make it a lot more powerful than just a regular Tegra X1.  I'm not sure if it would be as powerful as the Xbox One though, hopefully it is if they do decide to use a Pascal Tegra X1. I still want them to use an X2 though just because at least that would be definitely at Xbox One level, maybe even more, so there would be no concerns about power.

This. Or rather, UE and Unity both support iPhone. It's the game engine that supports the platform and not the platform that supports the game engine.

I'm going with X1 as shown in this video.

Like you say it has to be at least this powerful even if it's an X1, modified X1, or X2.

If it supports it, then should it not?

Its more about features than it is about power.