We never have either, but I've been on the DLR boards and there are a lot of WDW Veteran experiences and comparisons. For a few reasons, we have decided to give DLR our next vacation probably early Dec 2015.
The general comparisons seem to be that WDW vets are used to a BIG WIDE exclusive Disney World resort area. When you get to DLR, its literally in the middle of a city, which can be underwhelming for some who are used to driving under all the WELCOME TO DISNEY WORLD RESORT signs etc.
However, some people choose to see this as a plus. For many WDW vets, staying on property makes the trip much easier in that you can come and go, be close proximity, and enjoy extra hours etc. However, if you don't stay on property, this can be somewhat of a logistical challenge, especially if your hotel doesn't have good shuttle times or no shuttles, etc. In DLR, Disney only has 3 hotels considered ON property, but they have a whole host of Disney Neighbors that you can book right on the DisneyLand site and get basically some of the same benefits. Additionally, any 3 day hopper gets at least 1 day Magic Morning hour, as opposed to only property guests at WDW getting extra magic hours. If you stay at one of their 3 hotels, you can have them every day, same as WDW, but its not a requirement to get at least one. (This can help because I think AP holders don't get the EMH, and in CA, there are a lot of them.)
So basically, you don't have to stay RIGHT ON PROPERTY to get all the logistical benefits of coming and going as you would like to. They also say that DTD is super close, and here is a big plus: hopping they say takes less than a minute. You go in one gate and through the other. That means they go back and forth to take advantage of FPs etc (the parks aren't linked so you can hold them for both), and it isn't not very difficult to get back and forth. We spend a lot more time at WDW hopping in transit to the parks, I think a lot of times we underestimate it. I've even been stuck on monorails just sitting at the hotels for 20 min when we were only going from MK to EP, and then you have to switch at the Ticket Center, and don't even get me started on the last bus station stop at AK to hop to EP and how long it took for an EP bus to come...
They say that California Adventure struggled somewhat when opened, however, they have updated it to be a sort of Hollywood Studios model and look, which HS is our favorite, so that will suit us just fine. I can't remember which park has which, but it has a lot of Pixar things that WDW doesn't (Carsland, Monsters ride, Nemo subs). Not only does it have new rides that we don't, it is the clear winner on several World vs Land: POTC is clearly beloved at DLR, Space Mountain has all new track. (Somethings at WDW are better, ToT etc.) Add to the fact that they still have ALL of our favorites, and I've seen some Marvel Ironman tie-ins at their Innoventions, I've heard talk of them having Turtle Talk, Radiator Springs Racers being like their Test Trak, Soarin of course, TSMM isn't as big a deal with so many Pixar rides so the line is like 30 min, they even have their own RnRc California Screamin'. Dinoland becomes Indiana Jones, so excited about that too. They still have animation classes. There is a lot more going on then just the Matterhorn. Additionally, their World of Color show appears to be spectacular and they still have Fantasmic (no arena). They still have A&E and parades etc. They currently have a Rapunzel show that I am really hoping is still there when we go next year!
So everything we are seeing so far is a plus:
-Easier hotel and transport back and forth
-Easier hopping back and forth to both parks
-Almost as many rides as WDW, but located in 2 parks instead of 4
-NO FP +!!! I know there are some loopholes (some of them are out of the loop meaning you can hold a few at a time, the CA people know which ones they are) and you can hold FP for both parks at the same time, but it does require the sneaker method (going to the FP terminal) and not all rides have FPs. Still, not having FP+ tier limits and having to wait 80 min for TSMM!
Basically, if you love resorts, this may not be your place (although you can spring for the $$ for the nice ones on property if you want). But if you love to ride and ride, and avoid the peak days and holidays when so many locals go, I think you can get a lot of rides in. Someone posted that they could get 25 rides a day, which is how I'm used to WDW being (expect this year, obviously.)
We LOVE LOVE LOVE rides, and pretty much the only thing I think I'll miss this time is my beloved SSE and Showcase (both of which we got to do the last few trips in the last few years.) Otherwise, I'm looking forward to fresh scenery and all our favorites and easier access to them. At least that is the plan. I can't start planning it yet because I have to go after Election day (I work in broadcasting and Political Elections are killers), so it puts me about 18 months out but we are looking for probably the week after Thanksgiving next year.
That will give me time to get my Disney Rewards up, pay off some of this last trip (get 6 months interest free), and finish our flight rewards (we need about 12k more). We still get benefits like the free photo character session in DLR too being reward holders.
My BIGGESTT PLUSPLUSPLUS for WDW was eating like QUEENS gluten free this year. I haven't heard a lot about GF from posters at the DLR, but it being California, one would hope they are used to accomodating GF...I hope so...
So I hope that helps OP to see why people would even think to go to that 'other' Disney...
Oh yeah, on a side note, I also heard that Harry Potter won't be opening at Universal Hollywood until about 2016, and that is one of the reasons we have deliberately avoided Universal Orlando. USH still has Transformers, Simpsons and Minions, but no HP! So we are going to fit a day in there too before Harry Potter arrives.
California is looking like all pluses so far to me!