I’m thinking of breaking out my Pandemic Legacy S1 copy in the near future (all my other plans for playing it fell through), and it would just be me and my partner.
I imagine that we could take two characters each, so my question is whether that’s a good idea or a bad idea?
n.b. I’ve never played any of the P.L. series.
Well, @Lordof1 and I played it one-handed each and I didn’t think it was seriously broken (though we did mostly play the same characters, which meant they got loaded down with bonuses which we then largely forgot to use). I think the “bad thing happens after each player turn” game model is fairly self-balancing for player count, though I suspect with four pawns on the board we’d have spent less time travelling and more time Sharing Knowledge.
I’d go for two each, based on my experience of regular Pandemic. Our Legacy campaign we had three players.
I played all of the Pandemic Legacy games at two players, just one character each, with my husband and quite enjoyed the experience. Can’t compare it to four players or two players each running two characters, but just a data point to say that two characters worked.
We have played Pandemic 1 + 2 with 2 players and 2 characters each. I’ve always found Pandemic more difficult with fewer characters. But that may just be me. We usually played our characters alternating. And it worked just fine. Going to play Season 0 with the same setup 
In Season 2 we had a total of 5 characters that were actually used in the game. Except for 1 later addition we kept our starting characters and made them awesome
When I solo’d the game (before the online play through with @RogerBW ) I triple-handed it, on the basis I thought that would be easier and give me more options. It’s basically harder to cover all the trouble spots with more players, although having smaller players also seems to give more focus to the game so I’m not particularly convinced it’s much harder with fewer players. Certainly my playthrough with Roger didn’t seem any more difficult, if anything it was easier. That may be the fact that there was another person to bounce ideas off and that I’d already played it through before, although I tried to be very quiet when Roger largely guessed almost the entire plot very early into the game.
My wife and I played through Season 1 (and 2 and 0) with one character each, although we did consider two characters each. Ultimately we decided to go with one because my wife preferred not having to think through three other characters turns, to try and predict what the board might look like when it got back around to that characters turn again, when making a plan for the current turn.
We had a really good time with the game and I don’t regret our decision… although I’m also of the opinion that we would have had a good time with two characters each as well.
All I can think to offer as advice is:
My wife and I haven’t played regular Pandemic with less than five characters in a WHILE (we say we’re playing with our dear departed pets, the five of them share the three remaining characters). I can’t imagine we’ll change things around when we break out Legacy 1.
Just play with one character each. It doesn’t need more “gameness” added to it to be enjoyable.
I don’t think there’s a plot reason to be all four characters (unlike, say, the new Robin Hood) so I’d go for the one that’s just easier to manage.