I can´t see anyone with a true upper hand in winning this year but I reckon Spain should be the favourite only based on their quality in every sector of the pitch. Leaving Isco and Saul Niguez outside of the Euro is mind boggling, they would start in every other team probably.
In a playoff match I think defensive competence is the X factor and here I think Spain, Italy and Portugal are the top 3 teams this year.
As a portuguese I am really optimistic because we have a lot of young talent that can flourish and with this coach we finally play in a setup that excels our qualities. Excelent without the ball and very skilled with it on transition. We are a very mature team that know our limitations in the last sector (Ronaldo and Quaresma... Nani is shit and Rafa is still in the learning curve) and use our midfielders as much as we can.
Don´t be surprised with the quality of Danilo, João Mário, André Gomes and with the consistency of Moutinho. Renato Sanches coming of the bench is great too, his intensity is awesome (and I can appreciate him now cause he´s not a benfica player anymore eheh).
Going to the point of the last comments, I think I can help with an outside view of the England qualities and possible missing links to greater achievements.
Firstly I love that you guys can play with the Spurs backbone. We all do.
And you deserve the win against Russia that´s for sure.
But I think that England has a major deficit that can cost you in the big games and I actually noticed that in the game you play against us recently (in spite of us playing with 10 like 60 minutes).
Your team is very volatile and don´t know how to control the rhythm of the game. You have the better players on the pitch. But the team appears not to be mature enough to know what the game asks and when you have to make your qualities shine.
One thing we learn in practices here in Portugal is to play without the ball and when to attack it. To read what the other side is trying to do and to counter it. This is the reason why Portugal is so good in youth competitions (euro sub21, world cup sub20, etc). Our teams are super mature and controlling the tempo of the game is the thing which distinguish us from the technique of Spain, the bossy football of Germany, the fast pacing style of England football.
In my opinion, that´s why your game seems so disconnected at certain times. Players that know HOW to play but don´t know WHEN to play it together as a unit.
Sorry for the long post, but I really love national team competitions because of the clash of styles always so charismatic and fun to see. And english is not my first language give me a break!
Good luck to England, hopefully we meet in the finals and that game goes to penalties... I have good memories of English players facing our GKs from the spot