managed to squeeze in some testing tonight… uploading various avatars to bp and seeing the size difference between the thumb and the full..
with the various images I was uploaded, I am seeing about an 8:1 differential… so if I updated a 5k avatar (typically what I use and about what you would get from gravatar.com), I was seeing a BP full size image of about 40k…
so if you have 10-20 posts in a topic view page, that would be quite a substantial increase in image bytes downloaded… might even be noticeable…
but I clearly understand how you need the bigger image if you have an avatar larger than the BP thumb as it scales quite crappily…
so I think it will be a selectable option…
@Denis, if you wanted to look at some of your uploaded BP avatars and compare the thumb file size vs the full file size, that would be another data point…