I prefer thumbs, not that because I have a slow connection (30Mb) but because I can pick and choose which ones I want to look at in detail, I also like large pictures, anything less than 2000x1300 on the web has to be good or of particular interest for me to collect, but I do post to this forum at 1500 as I feel that's a nice compromise for those with slower connections or smaller screens, and I do post as thumbs to give users the choice to expand or not. Some forums I used to frequent only allowed 800x600, that's thumbnail size as far as I'm concerned and of little use to anyone with larger screens, but perfectly acceptable for those still with small screens I presume.
I habit this forum more than most now simply because of the image quality and virtually zero size limitations, other than file size which is perfectly reasonable, any half decent picture editing program can compress a *.jpg to well below the site limits and retain fidelity, I use Paint shop pro but InfraView is just as good if all you want to do is *.jpg compression.
Kindest