I don't think they will look the same at all. The point is it is better to start with too much information and throw away the less important bits, than to start with too little and to try and create the missing bits. We know that JVC's e-shift effectively gives approx. 4 million addressable pixels compared to a true 8.x mega pixel UHD display. But if you start with a full UHD image and take the most valuable pixels (through a process of sampling), you should end up with a better image than the other way around.
As for e-shift 3 vs e-shift 2....I get the impression they are fairly similar in terms of concept but that there is now an Auto mode to save you having to select the different presets and of course that it can cope with a 4K input.