Unfortunately, this approach will always produce very skewed results as the people that follow the Tweeter are only going to see their RTs, not their Favs, so the RT option has a very strong advantage over the Fav option.
What we really want to do is retweet the question but collect the response a little differently.
The easiest way to do this is to ask folk to RT Only for A, but to RT & Fav for B - the total RTs minus Favs gives the A result & the number of Favs gives the B vote.
Because the question is retweeted each time there is no skew to one option or the other. To recap-
RT Only for A.
RT & Fav for B.
Total A = all RTs minus all Favs,
Total B = all Favs.
A Twitter vote done this way is both fair and easy, once you've tried it :-)
There's another example here.
