Well, there is only one 750 left, the Suzuki. As far as which one is best, well since you asked it on a Honda Forum, I can promise you that you are going to hear Honda here and nothing else pretty much. However, the only way to tell is to sit on each one and decide which has the best feel to you, or if you have friends who will let you test ride theirs. All of them are so close in performance now that its really a personal preference.
Most all the 600 reviews you will read this year are going to say the GSX-R is the best bike out there with the 600RR right behind. I had the choice to get whatever 600 I wanted and picked the Honda. After you do a lot of reading you will find that the 600RR is very forgiving and all around the best choice.
Sup to you but I think you picked a bad place to ask this question as I am sure you are going to find people to be a little bias here.