For us it is deals, money, how long, season....
Our first trip we did ASMovies....had a good deal (they did the whole value, tickets for family of 4 for under $1600)...it was great but hated the bus sharing....
So we tried Pop (i forget the deal)...we loved that it had it's own bus...
We would have been fine value but our trip on 11 it was 15% off value, 20% of mod and 30% off deluxe....it put WL in our budget so we splurged and truly feel in love....
This next trip, we are going for the holidays a short 4 day trip with MK being park of choice 2.5 out of the 4 days with each other park getting 1/2 a day...we loved the closeness of WL but originally booked POFQ w/
free dining....this trip though we have changed hotels 4 times because two deals came out....after we did POFQ, we really looked at price and saw WL wasn't much more with FD...so we changed. Then we got 30% room discount and I have always wanted Poly...booked Poly CL for same price as WL w/ FD....again talked a lot about CL and uf we would actually use it and knew we wouldn't. Since we didn't want to pay for a service we wouldn't use, it came down to what hotel did we think was the epitome of holidays in Disney, WL or GF....we opted for less savings with GF but we want to be immersed in holidays...we are from Northeast so WL is fairly similar to how we decorate for the holidays around here so GF won out....I am still shocked that we switched as much as we did because we have never done that but again, so many factors go into it and each trip is different....
I hope to try Poly next time or a split stay that includes poly but will only do it with a room discount promo...my dream trip would be a ten day with an epcot/hs hotel for half and poly for the MK part of a stay.....but that will need a year and a half to save....