Personally I think its worth every cent, I am sure most would agree.
Disney cruises are more expensive, but its a premium for the Disney experience--Disney has the market share to charge more--simple economics. Also, the higher rates are also needed to make up for the lack of casino, and being a more "family" cruise they make less on bar-tabs/drinks etc. Still it's worth it to me.
I have sailed several other lines, and I prefer Disney over all, for several reasons.
1) It's Disney-- if you love anything Disney, you'll be in for a treat
2) The entertainment--both the evening shows and the cruise entertainment/activities can't be beat
3)Service--The service from the moment you get to port is second to none
4) NO CASINO!!!
5) Family atmosphere--just enough night life, but more class--not loud and rowdy at all. Want party-life cruise, take a Carnival cruise.
6) Staterooms are larger
7) rotation dining experience
8)Adult only facilities--a lot of cruises don't have these--adult only restaurant/spa/pool/entertainment/beaches
9)Checkin/Checkout procedures--easiest I have ever experienced
10)
Castaway Cay!!!!
As far as which 7 day, I haven't done the Disney 7 day yet, but if I had to choose, I would probably go on the Western, just because I am more interested in those Ports of Call.