An update, just because I'm in the mood. Apologies for the book.
I'm up to 19 games as each power against the bots, for a total of 133 games (results and stats, as mentioned before, at
https://docs.google.com/spreadsheets/d/ ... sp=sharing)
For purposes of this discussion, I'm going to equate the question of "best country" to "who is easiest to solo with".
For me, count of Solos by power:T:12,I:11,F:9,G:7,E:5,R:5,A:3. If I look at Solos + Draws, it's T:14, F:14, G:13, I:12, E:9, R:9, A:7. My solo rate right now is 52/133 (39.1%).
Turkey: Extremely straight forward, with a solo rate of about 63%, almost 2/3. 17 of my 19 games have started with Con->Bul, Ank->Con, Smy->Ank. All 12 wins were in those 17 games, which is a win rate of over 70%. You may need a little help from Russia around Trieste, but unless there's a very strong A/I going on (and given bot Italy's proclivity to attack Austria, it's rare) you've got a good chance and timing the stab on Russia is the main trick. Also, you do have to be concerned with getting stalemated, but that's only happened to me once (even though I probably should have been stopped a few times).
Italy: 19 Lepantos (I've never tried anything else). 11 wins, ~58%. Get all of Turkey, turn on Austria in Tri, Gre, and Bul, push toward St. P. and/or Mar/Spa/Por... hope France doesn't come at you at all (F/T is annoying to deal with) and hedge just a little against Austria having A Tri and moving A Vie->Tyo early on if you have to.
France: 9 solos, not quite 50%. Looking through my games I see a lot more early attacks by Italy that I would have expected - it looks like in 6 of the 10 non-solo games, Italy played something aggressive before the end of 1902. In only one of those games was I able to able to fend off Italy while not also getting attacked by E or G or both. Italy also attacked France once in 1905. France attacked Italy in 1902 and got attacked by E/G. (Two of the 10 were F/R/T draws.) Otherwise, when Italy doesn't get involved, it seems pretty easy to roll. France is tied with Turkey with being completely wiped out the fewest times and solos+draws. I still think France is pretty strong.
Germany: 7 Solos, ~37%. Germany seems to be my "feast or famine" country. There were only 2 of the 19 games where I finished with more than 2 but less than 18 centers... Looking back through the failures, there are some E/Fs, some E/Rs, and some F/Rs, and even a couple of E/F/Rs. The successes are widely varied... I have not yet done a deep/thorough analysis of these games yet to determine where I might have played better, but I seem to recall that the choices are tougher and more varied than the general strategies I've been using for, say, Turkey or Italy or France. (Do I let Russia into Sweden? Who do I ally with? Will they actually work with me? Who do I attack first?)
England: 5 Solos, ~26%. Again, like Germany, haven't analysed these in depth yet. Taking a quick look, I see that England has survived a few southern power victories (whereas I have never survived a bot win as Germany). In general, it looks like France's strength is England's weakness... none of the English solos involved a F/E. There were times when I would have liked to do an F/E, but haven't figured out how to convince France of that - France seems to be very inclined to go for Lvp eventually, even if you can stop him from getting it once and he backs off. It appears that E/G is much more workable.
Russia: 5 Solos, ~26%. Very similar results to England. The only thing the successes seem to have in common is being allowed into Sweden in 1901. In those 5 games, only 1 had an R/T alliance that survived until the end of game. In the other 4 solos, Turkey attacked R first in two of them. A couple of the wins has Russia going after Turkey only when Italy had started a successful Lepanto, then kicking Italy out. In the other 14 non-solos, Turkey played Smy->Con->Bul, Ank->BLA in 9, Con->Bul, Smy->Arm, Ank->BLA in 4, and Con->Bul, Ank->Con, Smy->Ank in 1. Of the set of 9, Turkey attacked Russia first in 6 of them, Russia attacked first in 2 of them, and neither attacked the other in one. Turkey seems to like his 1902 attacks, it looks like there were three of those. Russia also had issues with German incursions and dealing with England as well.
Austria: Ick - only 3 solos, a paltry 15.8%. If the board breaks correctly, it's possible - the easiest start would be where Italy attacks Turkey and Turkey attacks Russia. I have not figured out yet (as I mentioned in another post recently) how to get R/T reliably on side (I know I've at least tried a few times but probably not every time) whilst fending off Italy... if Italy and either Turkey or Russia even remotely touches you - they don't even have to take anything, just cut a support (which they seem to do more often than not) - then it's all over.