For all the positive reviews about the leaked PES demo, I have been reading complaints that indicate the jury is still out on just how much the game coding has actually improved. The game looks fab in motion, there is no question about that. It's also obvious the CPU AI is miles better than any football game to date with regards to on-the-ball movement. But I've also seen a number of goals scored where the GK AI looks as broken as ever. There have also been plenty of complaints about Konami's infamous scripting, something I've been worried about since they announced their Heart feature.
I'll wait for the PC demo, and I will play it and read user reviews in the meantime. But given the past several years, I would never consider pre-ordering or purchasing day 1, regardless of how amazing these videos look. And in all honesty, I don't think anyone who knows football would ever state FIFA is a more accurate sim. The thing with FIFA is that, up until this year anyway, people have gravitated towards that game because of the licenses, because of the smoother player control, and because the game in motion looks better than clunky old PES with it's PS2-era animations. For most gamers, licenses, gameplay smoothness and great animations = more real. IMO that's what people are actually referring to when they say FIFA is more sim.