In terms of resort prices, 7/6/18 sees a tick down in many resort rack rates (value season) which lasts until late August. It obviously varies on the resort and other factors, but July can often be a touch cheaper than June, generally speaking.
Just to put some real world numbers on that statement… the Poly Standard Room rack rate for all of June 2018 is $526 per night. It’s $499 starting 7/6/2018. Although this same logic doesn’t apply to all resorts – eg, Pop has the same rack rates for both June and July. So it really depends. Discounts could also alter this logic as well.
As far as crowds, we’ve done the last week of June, July 4th week, and the last week of July over the last few years and they’re all pretty much shades of grey in my mind. No one winner over the other.
The weather data probably shows that it’s hotter/wetter in July over June, I suspect.
Hope that helps!