I personally favour the Alternative Vote system because
1) I think maintaining the geographical link between constituency voters and elected representative is key to the way our parliament works. That's why I disagree with the Single Transferable Vote - that link is broken.
2) AV allows a candidate to get 50% of the vote, and that's key for me too. I think we should either go with the French system where if no-one gets 50% they should have another go, or take the second (or even more) preferences and stack those up. Now I personally would go with second only because
3) it's relatively simple. I remember at school my teacher talking about the various systems. One where voters are allowed to rank all of the candidates gives those who vote of one of the leading 2 one vote, while someone who ranks every single candidate can have numerous votes. This was tackled by the first vote counting as one, while the second would be a fraction of one, the third a bit less and so on. so I'd rather there was a 1st preference which could be for the winner or a smaller party, then a second preference for a major player. Maybe a third, maybe not. We have three major parties, so voters should probably get the chance to rank those three if they so choose.