The Poly is the busiest of all the WDW Deluxe resorts, It's the one everyone wants to stay at when choosing a monorail resort and it is also the one that everyone who goes to MK for the day chooses to pop over and visit or to dine at. We never choose the Poly for this reason.
Universal will be cheaper and quieter UNTIL they have the same amount of parks as WDW, Uni has 3, WDW has 6 and Golf Courses and a much larger shopping district. To me, you can't compare the two as they are so very different, WDW has massive crowds because of the sheer amount of things to do there. Example, we spend 20 nights typically at WDW property and only 4-5 at Universal and of those 4-5 at Universal one or two days is spent at other parks (Seaworld, Busch etc) and I know many other people who do the same thing.
I LOVE Universal and always incorporate it into a trip and it is so nice to have that other side of a vacation, but to flat out compare the two against each other is impossible because of the differences.
I must say that I do agree that Poly is a popular deluxe resort. We loved the resort, but just came away feeling like we overpaid when we compare it to a deluxe resort at Universal that was half as much. We do still plan to visit both parks on our next trip, but will most likely stay more at a Universal resort next time.
This is why we choose the company we go with they have a protection plan that is very inexpensive OR just get travel insurance - either way you're covered if you need to cancel or change dates etc. The thousands of dollars in savings are 100% worth it for us over the "maybe" risk of having to cancel.