I've been to WDW and DL as well as DLRP a few times.
DLRP in my (and most peoples) opinion is the prettiest park.
The castle (pink!!!) is my favourite, although I like that the WDW casle has CRT and the suite and stuff in it. The Ca castle is wonderful as it was the original, but it's a little underwhelming after the other two.
Also i loved DL but found the older attractions (matterhorn!) made the park seem a bit fairgroundy to me...
I also think discoveryland is much nicer themed and better looking than the other parks tomorrowlands.
They do all have their good and bad points though - such is the beauty of life.
If i could visit and for free, I'd choose WDW, but I love dlrp for the caslte and detail and i think it has the best rides, but it think DL will always be the one with most meaning and sentimentality.
Londgwinded, i know!