A quick glance at the 3 gentlemen's campaign websites seems to indicate that Mills is the most intellectual of the bunch, and has written a series of articles. Emery looks like he's better suited to federal office (his last campaign statewide was in 1982, in the infamously disastrous contest against appointee George Mitchell), so I'd be wary on that alone. Woodcock claims to be the most Conservative of the 3, but doesn't have as comprehensive a platform as Mills does. So from those, it appears Mills is the best of the bunch as being the best informed.
Actually, his loss to Mitchell doesn't concern me, I see it as a plus. Mitchell was the incumbent, even if appointed, and it was a D year in a D state, and he was a very good candidate. It was unlikely that he was going to win.
But the fact that he's run before means he knows how to campaign, has the connections, and knows what to expect in a statewide race.
Mills articles look decent, but his campaign website looks horrible, and he's also in his 60's, and voters don't often elect people to statewide offices, for the first time, much past 60. Also, he doesn't have as much experience with large campaigns.
Woodstock seems to me to be a 2nd teir candidate.
I think I'd support Emery from what I can tell from their websites. Although Mills seems decent, it seems to me Emery would be a stronger candidate in the general.