I have a 2p account and got it up to the mid-20's, but then I found I was obsessing over my rank too much and so decided to play a bunch of unranked games under this new alias. I soon found I enjoyed the 3p/4p games quite a lot, and so decided to register the account, and my ranking soon shot back up to the mid-20's. All of my ranked games with it are 3p/4p. It's especially convenient with the gmail and yahoo options: gmail is 2p, yahoo is 3p/4p, and I just click on the account type I want.
I find that player psychology is a lot more important in multiplayer games. The lowest-ranked player can end up being a kingmaker, and being aware of this adds a neat dynamic. If that includes them resigning, then so be it... at least it means I won't come in last place. The 12 provinces or colonies vs. 8 isn't such a big deal, you just have to accomodate more cards in your deck. Besides, if there's 2 people left, I get to play 50% of the time, and that can be a slight quality-of-play bonus.
There are games I've lost in 3rd place against two level 0's that I would never lose in 2p. I wouldn't say it's because 3p/4p is more swingy, it's just that you generally need more than card counting and minmaxing to win. I wish more high-level players would play 3p/4p... then I could restrict the opponent rank to +/- 5 levels like I do with 2p. Things I like about multiplayer are that all attack cards become more interesting, and choices about cards that involve the player to your left or right are also interesting, because their effect can depend on the skill of those players, e.g. smugglers, possession, and even envoy.
Back on topic: the only type of resign I find aggravating, even in multiplayer games, is when I have to wait for 3 minutes. It's possibly worse in multiplayer games because then 2 or 3 people have to wait for 3 minutes. I think that in an unknown number of cases it isn't because the person is being passive aggressive, so I'm not going to comment on whether they're being rude or not. Maybe they just close the tab without thinking about it. I'm not sure what the exit link does. If it's the same as resigning, why bother having the resign button at all? (I've never resigned from a game except once when my connection died.) And since I can force resign people in the middle of my turn, I think anyone should be able to resign at any point in the game; having to wait for the beginning of your turn seems arbitrary and more likely to induce the 3-minute timeouts.