I always try to go as mathematical about Diplomacy as I possibly can, so I am probably 100% classicist on the romanticist-classicist axis and I also love the social element, so I'm probably a club type.
The way I see Diplomacy is a predator/prey model. If you win, you have 6 prey and 1 predator, let's say you have a score of 6, which we can normalize to 1 (divide all scores by 6). If you're in a two-way draw, you have 5 prey and 2 preditors, your score is 42%. Notice that it's not 50% of a draw, but less than that: not only do you have to divide the loot with one more player, that player himself is no longer part of the prey pool.
So when I doubt between going for the solo or the two-way draw, I estimate if the chance of soloing is more than 42% (so even if it looks a little worse than a coin-flip I'll still do it) in which case I go for it. The decision can be rationalized for any dilemma you face that way.
The art of diplomacy, for me, is to completely leave out feelings. Be sure not to offend anyone, but also be sure to never be offended. And always optimize your result. That's my 10 cents.