Under both systems you say which candidate you like best, and under AV you can also put the others in order, so if your favourite candidate doesn’t have a chance of winning you still get a say. AV doesn’t completely eliminate the scope for tactical voting, but there’s much less of a dilemma between voting for your favourite and trying to influence the result. That dilemma’s pretty commonplace under FPTP. It’s not the only reason I’ll be voting for AV, but it’s one of them. Other reasons are that FPTP makes two-party politics more likely and creates more safe seats, that under AV it's even harder to win if most people hate you and that if the voters get to say more at the ballot box then the parties have to work more to influence what they say. For example, consider someone who pretty much always votes Labour. The politicians can more or less ignore her, because Labour are more or less guaranteed her vote and the others haven’t a hope. Under AV the other parties can work for her other preferences, and Labour can’t ignore her either because she’d be less reluctant to put someone else first if she could still put Labour second. Other things being equal, the more information the electorate can supply, the more work the politicians have to do. That means more accountability, and accountability is the reason democracy is better than all the other systems we’ve thought of. Unless you’re a big believer in the wisdom of crowds.
AV isn’t my favourite voting system, but I like it a lot better than FPTP, and that’s what we’re being asked about tomorrow, because the Tories are scared of asking us whether we’d rather have proportional representation, and nobody who counts has thought of this system yet. So tomorrow I’m voting Yes to AV, and if you’ve got a vote I’d like you to do the same.