Wales and Ireland is always the same, a bounce of the ball, a referees decision, a mistake is normally the difference.
I'd make Ireland favorites simply because Wales always start badly and finish strongly. The Welsh players normally have to be terrified of failure and for the Welsh public to start getting angry with them before they pull their finger out and start trying.
As usual I don't think there is going to much between Wales, Ireland, France and England.
I've no idea what to make of England with Eddie Jones in charge, Eddie Jones never seems to have his teams playing at the correct level for their talent, their either terrible or over achieving in spectacular fashion. I do think Eddie jones is going to want to have some retribution against Wales, he got a little when Japan beat the Welsh third team during the last Lions tour. but I don't think he'll ever forgive us for getting him the sack when Wales beat Australia last time. 
I'm not holding out ANY hope for Scotland, despite all the talk about improvements etc... bottom line is Scotland haven't actually beaten ANY of the old 5 Nations, or the old Tri nations, since their 12-8 win over Ireland on the 24th February 2013! No shame in not beating South Africa, New Zealand or Australia, but to not beat Wales, Ireland, France or England for three years is bloody awful! Basically all their success has been against Italy, USA, Canada and Japan who they always try to play regularly. Wales have actually won 12 of their last 13 against them, with the only loss being when Gareth Jenkins was coach!
Wales haven't lost anyone of note since the World Cup to retirements, truth be told we probably increased our strength in depth during the World Cup. Put bluntly we should beat France, Scotland and Italy all at home, and it's not beyond the possibility that our experienced squad could take out England (again) at Twickenham, especially with an inexperienced team, and new coaching set up. Wales have a terrible attitude problem, and seem to look stale and bored at times, then basically Gatland has to threaten them that if they don't buck up they won't play for Wales again, then suddenly we look dangerous and determined. Hopefully Wales can skip the lazy part this season.
France, I don't think it's going to work out for them this year. To me, putting Guy Noves in charge of France is a bit like putting Alex Ferguson in charge of the Scotland football team. Noves built Toulouse around him to the last detail, he won't be able to do that with France. He was coach of Toulouse from 1993, to 2015 and had a magnificent career, coaching some of the best players on the planet, however i think only 4 of his squad are from his old club team and I can't see the new players simply accepting him as France's savior. All of the previous French coaches in recent memory have been former internationals, with massive prestige in the French game and none of them have inspired these lazy, untalented, disinterested French players.
Ireland have been to good for too long, I hope to god they start to tail off a little! They lose Ronan O'Gara and Sexton appears. I'm hoping losing Paul O'Connell leaves a massive gap, but someone will step up. It's going to be an interesting year for them.