dialog speed issue 1.7.2 -> 1.8.0

dialog speed issue 1.7.2 -> 1.8.0

I recently tried to omptimize the javascript on one of my web pages. When I benchmarked all my dialogs they took 300ms. So i descided to change my jqueryUI version from 1.7.2 to 1.8.0 in order to see if it would lover the delay. However the time it took to load the dialogs became 700ms instead. 

Do anyone know of any reason which would make the load time more than twice as big?
I tried searching for people with similar problems but couldn't find any.