Granted the full game is the same as the demo, it will be a love / hate relationship.
There are many good things in this game, many improvements over both PES 13 and FIFA 13, but there is a list of game breaking issues (wingers' unrealistic speed bursts, defenders catching up quick forwards, floaty shooting) which if unresolved, will ruin the game (arguably it already has).
It is clear that Konami will not have time to sort out these things for full game release, but they really need to get their finger out and patch the issues. If they do so, this will be an amazing game.
Regarding the competition (cough-cough 14), I have to say - I hated their demo at first and I thought - here we go again - same old). But after spending some time with it I am beginning to appreciate some very interesting innovations. Players now have weight and momentum, which are really noticeable. Ball possession is extremely well implemented with players making all sorts of intelligent runs off the ball, including coming back deep to offer an option. It feels realistic and more importantly it is useful. As such, the game is very enjoyable when the user is in possession of the ball. Through balls, passing and especially shots are amazing to watch and a well constructed move feels real, weighty and rewarding. And it feels like football.
The downfall of FIFA is (and always has always) the defending. This year is similar. The CPU will turn and twist way too quickly and unrealistically. There is no way the user can contest this and you only rely on player positioning and CPU's error. However (in contrast to PES 14), the user controlled defenders are much more responsive and quicker, which lessens the frustration. Also, FIFA has tightened its slide tackle control/animation, which is now very useful and rewarding when used timely.
In summary, both games have made some noticeable improvements (weight, momentum, player runs off the ball). With a better presentation FIFA 14 would have been amazing, but the recycled graphics, over-saturated colours and identical player models (lack of individuality) let it down. Defending is also frustrating.
KOnami has done a great job with PES 14, introducing the concept of weight shift, tightening the gameplay and resolving some past issues, but they are guilty of marring the experience with some inexplicable errors, such as the unrealistic speed bursts (mainly focused around CPU triggered through balls) and the artificial catch up by defenders. Shooting is also extremely annoying, which takes away from the oomph and the pleasure of scoring. With a patch, PES could be amazing, but knowing Konami, I don't have high hopes.
Which leaves one with the wishful thinking that the two development teams would get together and implemented the best of both worlds. Then we would have been for a real treat.