Yeah, from what little I've seen on these internets it looks like EPCOT's 30th was a bigger deal than WDW's 40th. That could just be my EPCOT bias though.
As someone who attended both, no question - Epcot 30 blew WDW 40 out of the water. Epcot 30 was a two day event with tons of D23 support. WDW 40 was a parade and a speech from Meg Crofton. Ew.
I knew if this business was ever to get anywhere, if this business was ever to grow, it could never do it by having to answer to someone unsympathetic to its possibilities, by having to answer to someone with only one thought or interest, namely profits. For my idea of how to make profits has differed greatly from those who generally control businesses such as ours. I have blind faith in the policy that quality, tempered with good judgment and showmanship, will win against all odds.
D23 actually staged a much bigger event for the WDW Resort 40th than they did for Epcots 30th, but it was held almost 5 months before the October 1st date in May of 2011. While I enjoyed the D23 Epcot event, their Destination D event for the 40th was far more in depth. It also featured R Sherman on the piano and Dreamfinder in costume singing One Little Spark. The icing on the cake was the CM choir and orchestra featuring a medley of WDW music.
As for Oct 1st celebrations in the parks, both had short ceremonies, but Epcot blew off the lid when it came to the fireworks!