If I had to pick between Eastec and IMTS, I would go to IMTS. There are a lot more machines on display and a lot more tooling vendors. Although there won't be too many regional vendors from the east coast with their own booths.
If your interested in screw machines, Swiss, and mainly bar turning, PMTS would be a better bet.
Here are the dates:
PMTS April 24-26th Columbus, OH.
http://www.pmts.com/
Eastec May22-24th Springfield, MA.
Eastec web site
IMTS 2008 September 8-13th 2008 Chicago, IL.
http://www.imts.com/
I'll be at PMTS and IMTS. Not sure about Eastec though.
Hey if you've got someone footing the bill, maybe you should check out EMO. It runs from Sept. 17th-22nd in Hannover Germany.
http://www.emo-hannover.de/homepage_e
Or wait until 2008 for JIMTOF which is held in Tokyo, Japan.
http://www.jimtof.org/Eng/
I've been to them all and IMTS and JIMTOF are my favorites as far as the show itself goes. EMO wins for location. The reason I like JIMTOF is that the builders still show prototype machines there. I've seen some funky/weird stuff at JIMTOF. EMO is just huge and you'll see a lot of builders that you didn't even know existed.