Moan, I have one at each of WHS and PHS.
Obviously, it all depends on so many factors and only you really know what would suit your DD and your family best, but I'll give you my opinion anyway!
Until a couple of years ago, I'd have gone with PHS as the pastoral care at WHS was dire. However, since the change of headteacher, I'd go WHS without hesitation. The ethos of the school and the attitude of the girls has changed dramatically. Academically, there's very little between the two, but for me WHS now wins hands down. The head knows them all by name, has a very good idea of who needs praise and who needs a kick up the @rse. She spends time in the classroom with the girls every week and they adore her. As a family, we've had various issues over the last few years which have affected our DDs. We've always kept the headteacher up to date. PHS rarely reply to my concerns, whereas WHS have not only replied but have gone out of their way to help.
My DD at PHS wants to move to WHS after her GCSEs next year, as do a couple of her friends. To be fair, she didn't get into WHS at 11+ (well, she was on the waiting list but we were too impatient to wait and thought they might be better in different schools anyway) and once her hormones kick in properly, she might prefer co-ed for 6th form anyway!
Good luck - it isn't an easy choice but you're lucky to have a choice at all.