Hi, marien - G O's Senator chronographs still use . . .
By: Dr No : September 16th, 2010-10:57
. . . the cal 39 base movement, which are of modular construction. The integrated chronograph movements - cal 60, cal 61, cal 95 - have never been utilized in the Senator line. An updated automatic chronograph movement based on the cal 100 seems a natural development, but I don't have any news to report, unfortunately.
My first G O was a Karree chrono that garnered admiration from many, including two complete strangers that were taken by it's appearance. It also ran exceedingly well, and cemented my devotion to the brand as a result. Tony A recently acquired a Senator Chrono XL, and Jocke has an earlier Senator chronograph - perhaps they'll stop by and give you the benefit of their experience.
I also admire the Zenith EP, which has outstanding technical credentials; I've considered a recent model myself, but have been pursuing vintage watches recently, and more inclined in that direction at the moment. The EP would be marginally useful for my purposes as I rarely have need of it's precision; the only time I really use a chrono is when attending endurance races, perhaps once a year at best. The reason for leaning towards a Senator (or Karree) chronograph would be more aesthetic than technical, in my view. If I were in your place, I would be asking whether the perceived technical advantages of the EP that would be in play for relatively brief periods of time outweighs a presumed aesthetic preference for a Senator chronograph model.
Cordially, Art