I think that if you make the size higher on your JPG, you will have the same quality of a PNG. I find it pretty useless to save it as a png =\
Well there can be transparency when you save it as a .png and its a larger file size when you save it as a jpg no transparency but the file size can be much smaller and you can change the picture quality when saving in PS In my opinion when I save it as a jpg at 12 quality its not worse quality then png so thats what I do
PNG-24=ubah. Plus if you have a copies folder like me, it'll go straight to that folder, so you don't have to go through the catacombs of your system to find the copies folder likr you do with JPEG.
i still save my sigs as jpg though. png takes longer to load. first its blurry and its sharpened all the time.
personal use I'd say png but if you're going to use it as a sig pic/avatar/forum pic, jpg, as it will take a long time to load for people who have slower connection speeds. There are already many pictures to load what with all of the signature pictures etc.