If I get to vote, I pick pic #1. Thumbs over full size every time!
I prefer Safari and the Old Galleries so I learned to create thumb links by hand.
Open your gallery, click on a thumb. Under "PHOTO DETAILS" copy "LINKED THUMBNAILS" And paste it in your post. This thumb will bring up the ENTIRE IG gallery database and every picture in it (not just yours, everyone's), takes some time to load and shows a reduced image.
If you quote me, you'll see the LINKED THUMBNAIL address above contains 2 http addresses. Copy the second, paste it over the first, remove "thumbs/" from the pasted address and it will now take you straight to a full size shot sans gallery
Again, if you quote my post, you'll see the differences between them.