Go to a Sony store and try the devices themselves. Bring a file with you and get them to let you try it. As for Wifi- neither the Nook or kindle have it.
For PDFs -Dont take my word for it since I sell them, read the other reviews here by owners- I really suggest the PocketBook models. The PDF support is quite possibly the best available and is one of the reasons I wanted to carry the line.
Of course the PocketBook 302 will be out soon as well as other models as you mentioned. If you are on the fence now it might just be better to wait until after CES.