I'm trying to choose between those same two sets. They're both excellent performers, and both produce a hugely likeable picture... I was impressed by both of them. One thing though is that I have only seen the Sony showing Blu-ray and not Freeview, so I don't know how it performs with standard-def content, whereas I have seen the Pioneer displaying both Blu-ray and Freeview content and left me well impressed with both. I know that I will have to go back to the stores and have another look. It's a shame that there doesn't seem to be a store that stocks both, so I can't do a side by side comparison. I'll just have to try and remember well.
Anyway, I feel maybe a little bit inclined to go for the Pioneer because I love the way it looks, and I was amazed by it's images from the first time I saw it. That said, I was very impressed when I first saw the Sony set too. And the Sony also looks cool - although I'm not really a fan of the 'midnight sky' paintjob which reminds me of some chocolate bar containing specs of biscuit or mint or something.
Another thing I have found is that the Sony set, like Sony sets in general, has quite a different picture; it seems quite cool and slightly unnatural, although I have always appreciated Sony's high-end sets for just having pictures that are different - a change - from plasma. The Pioneer has more of a warm quality to the image, and the picture is closer to that of a plasma. The Pioneer's picture also is very glossy, which is nice.
Please let me know which one you go for, and I'll do the same...