Yeah, big difference, but in truth I don't use HEVC much. However, it's good to know 1080p HEVC can play smoothly on an iPad Air 2 even though it's playing purely in software. Impressive, not only for Infuse, but also for the iPad. I wasn't expecting this.
Another reason there is no need to upgrade to the iPad Air 3.
I suspect it would choke hard on 4K HEVC, but that's something to worry about a few years from now. By that time I may be buying an iPad Air 5 or something.