Assuming it's still (or was ever?) true, the tally is "weighted" based on the relative populations of each nation, in order to try and balance it out. It makes it really tough to take many zones that are often used exclusively be a specific nation, like the Saruta zones. Not to say it's impossible, of course - even Windurst occasionally nabs the other zones. AFAIK gil/armor contributions don't matter. In fact, the only time frame that matters much at all is the last hour or two before tally.
That said, if they haven't been fixed, we were able to demonstrate that some zones can be 'flipped' at the last second by just getting the last exp-yielding kill right before tally. I'm *pretty sure* that's not true everywhere (and it may not be true anymore, and may have just been dumb luck). Either way, if you're gonna make the effort, get a party together from one nation and get an exp party going on Saturday night
