Adult bottles vs baby bottles

Hi angels! So I've repeatedly stumbled across adult baby bottles. It has a longer, slimmer nipple and I just wanted to ask what the difference was other than its appearance? Does it fit better in the mouth?

A bigger nipple is a more comfortable fit for most adults. We have bigger mouths and tongues and it provides a more substantial surface to interact with. I liked these: http://www.fetware.com/nuk5-nipple-wflange-p-89.html but the last one I had was too thin and frequently collapsed on itself when suckling. I haven't tried any of the more conical ones I've seen as they don't appeal to me by their appearance.

I prefer the adult bottles. fits in my mouth easy and I dont have to suck harder to drink.