We are WDW vets, who have been heavily considering purchasing DVC there. We always stay on property at WDW. However, DL has been on my bucket list, and we just got back from our quick trip. We were there from August 13-17, we stayed at the DLH, and we had an amazing time! I would highly recommend going. Our family had a terrific time enjoying both the similarities and differences between the two parks.
We loved riding the things that are the same in both parks and comparing the subtle and not-so-subtle things between the two sets of rides. We also loved checking out all the rides that DL has that WDW does not. It was AWESOME to be able to walk between the two parks and walk back to the hotel off and on throughout the day. Easy peasy! We didn't have to build in travel time for park hopping or going back to the hotel, which left more time to enjoy the parks. MaxPass is phenomenal...I really wish WDW would scrap FP+ and bring in MaxPass. We felt we were able to ride so many more things (so many more times) and wait in reasonable lines (in AUGUST!) with this. Totally worth the investment!
We felt all the feels that we feel at WDW walking down Main Street and being in the Disney bubble. While I don't have a California off property hotel experience to compare it to, if it's in your budget, I would recommend staying on property. The DLH was terrific! Beds were comfy, our view of the DTD and the fireworks was incredible, the room was large, and the bathroom was set up well for a family with two teenagers. It felt every bit like a deluxe property at WDW. We'd love to go back sometime and experience the Grand Californian someday, too.
It was really fun to see characters walking around the parks! It never got old...we saw Maleficent several times, Mary Poppins and Burt, and Red from Pirates of the Caribbean (I got to chat with her...she was so much fun!). That NEVER happens at WDW! We loved the summer weather too. We went to WDW last year in June, and it was so hot and humid and it rained a few times while we were there. Riding wet rides made hot ponchos a necessity. Not at DL! Yes, it was blazing hot, but we never used ponchos once. No rain, and we were dry from wet rides in a matter of minutes every time!
A few things we missed included the Disney meal plan. We have always used the regular meal plan at WDW, and with no meal plan option it was an adjustment to pay out of pocket for everything at DL. We realized we really like the all-inclusive feel that the meal plans give us at WDW. We also missed magic bands. Because we stayed on property, we were able to charge most things back to our room and then pay the balance off each day with gift cards. So, it wasn't a big deal, but it was something even our boys noticed and mentioned. Those magic bands make everything easier at WDW.
We noticed differences in CMs between the two parks. WDW CMs are more in your face (in being pleasant and greeting you everywhere you go, which I like and in being bossy by telling you to move forward and fill in gaps in queues, etc. which I don't always like) and more plentiful EVERYWHERE. CMs at DL are more laid back. We never had a bad experience with a CM at DL, but there just weren't as many around and they were just more "chill" and didn't seem to tell you what to do as much, which was nice. A down side at DL is that there were virtually no photographers to snap pictures (even on Main Street!) and when we had a question, we had to work a little to find a CM. Once we did, everyone was nice. So, CMs were not better, not worse, just different between the two parks. And, we have a lot of awkward family selfies from this trip.
We found the food to be virtually the same in both parks. We had some great meals and some meh meals at DL; that's also our experience at WDW every time we go. For TS experiences, we had a terrific meal at Steakhouse 55, we had a great experience at the Blue Bayou, but the food was "meh". We also ate at Naples Ristorante in DTD and it was good but not great. Some quick service meals were really good, and some were meh. YMMV.
So, the short answer is definitely GO to DL and if it's in your budget, stay on property! You'll have an amazing time! If we are in California in the future, we would definitely go back to DL. It was really special to be in Walt's park.