When they're small, you appreciate the smallness of them. When they're big, you appreciate the bigness of them. You are only hurting yourself if you start to hope for big tits when you are looking at small tits, or hope for small tits when you are looking at big tits. It's like when you are eating a pizza you don't suddenly start to hope you'd have a hamburger there, no, when you have a pizza you damn well enjoy what makes pizza a pizza. If theres some heavy hangers right in front of you, you better get into a big natural appreciation mode. If there's some perky small petite tits right in front of you, you better get into a flat tit appreciation mode.
Even if the women are clothed, there are boundless possibilities in boob appreciation in both the big and the small situations. It's a sexy sight when you can barely see the shirt has boob bumps, and it's a sexy sight when all you can see are those mountains on the shirt that jiggle like a castle made of jelly on an earthquake with every little movement by the woman.
Now that said, there is some unnatural and unnerving in a situation where the boobs are huge but they move like a concrete block buried in concrete. Now that said, it's not impossible to get into the mode of balloon boob appreciation either.