Asking people to vote on their preference and putting the thread in the SH3 forum is a bit like asking people at a Republican rally 'How will you be voting?'
I play both, but personally prefer SH3, mainly because I prefer U-Boats, SH4 is buggy, but it potentially has a lot more going for it than SH3, so I'm playing an SH4 campaign at a slow rate and watching developments with interest.