If you want to go from Disneyland to California Adventure, you can do so in about four minutes. You walk out of Disneyland, past the ticket booths, into California Adventure. The gates of the parks are literally less than a hundred yards apart. You can easily go from Disneyland to California Adventure and back multiple times in a day if you want to. And people do. For food, for fastpasses, for shows, the Electric Light Parade, etc.
Park hopping at Disneyworld can take 30 - 90 minutes, depending on what time of year/day it is. Seriously. The process is this: walk out of Magic Kingdom. Get on Monorail. Get off Monorail. Get on tram. Get off tram. Find your car. Pack up everything. Drive out to Magic Way. Find new park. Park car. Unpack everything (your stroller, bags, kids, etc.). Get on tram. Get off tram. Walk into new park. That's if you aren't relying on the park bus system to get you around. And if you don't have to wait in line for monorails or trams.
Blue circle is the Magic Kingdom. Orange circle is EPCOT.
Staying at a Disneyland Hotel (there are only three) means you are within five-minute walking distance to the theme parks. That walking distance is filled with Disney property, so you sort of feel like you're already in the parks. Unless you stay at the Grand Californian, in which you can walk out of your hotel lobby straight into California Adventure. That's, like, a fifteen second walk. (Pro tip: Anyone can walk into the Grand Californian. Go through there to see a much shorter security line to get into California Adventure.)
Staying at a non-Disneyland Hotel doesn't even mean you're far away. Lots of decent, cheap motels are less than a half mile from the front gate. As a kid, we always walked from our hotel into the park. It's completely reasonable.
Staying at a Disneyworld Hotel means you have access to their bus system to get you to the park. During the hour before and after park opening and closing, you'll wait for twenty or thirty minutes to even get ON the bus. Or you can drive yourself, since you get free parking. It's still a ten minute DRIVE. Plus trams.
Staying at a non-Disneyworld hotel means you're "a mile" from the "park entrance." This really means you're a mile from the border of the private property owned by Disney. You're really a twenty minute drive from any park, best case scenario.
There's no Indiana Jones in Florida. (The closest thing is Dinosaur at Animal Kingdom). In California, the Pirates of the Caribbean is longer and more story-oriented. You sit side by side on Space Mountain. There's no Matterhorn in Florida. California's Autopia is longer and has cars designed for kids to be able to actually reach the peddle. The facades - particularly in Fantasyland - are more detailed and imaginative.
I'm sure I don't need to tell you that Disneyland is on the left in all of those pictures.
Disneyworld is a lot bigger. The walkways are wider and longer and there is a lot of space between rides. Some people put this in the win column for Disneyworld, but I disagree. Let's just compare apples to apples, and take Disneyland in California versus the Magic Kingdom in Florida. Let's even pick three rides that are in roughly the same places in the parks: Jungle Cruise, Pirates of the Caribbean, Splash Mountain.
In Florida, I stop at the Jungle Cruise. I must park my stroller in the stroller parking near the Tiki Room. Then go down some steps to the ride. When I exit the ride, I will go up the steps, walk past my stroller and a street show to get to Pirates. Then I will exit Pirates, go back past the entrance to get the stroller. Walk back past a street show, Pirates, two sit down restaurants, a full store front, several kiosks (depending on the time of year, this number varies), a fast food place, a character meeting spot and walk around the entirety of Splash Mountain to park the stroller, double back and get in line for Splash Mountain.
In California, I park my stroller at the entrance to the Jungle Cruise. When I exit the ride, I am at the entrance, so I grab the stroller, go past the entrance for Indiana Jones* (though to be fair, I'd probably ride that ride while I'm here), park the stroller at the entrance to Pirates*. When I exit, I'm pointed right toward Splash Mountain, and the park is small, kids can walk this far. So you walk past the Haunted Mansion* (again, you'd probably ride this ride) and jump in line for Splash Mountain. The line winds in front of the ride, so there's no need to walk around the whole thing to get on it.
Disneyland is smaller, more intimate, easier to navigate, less easy to lose your kids, easier to let your kids walk 90% of the way. That makes it better. More crowded in peak seasons? Sure. But you shouldn't go to any theme park during peak seasons anyway.
*These rides are all "beyond the berm." Disneyland has a berm built around it to protect it from prying eyes during construction and keep out the "real" world while you're in the park. Space inside the berm was limited, so these rides are actually underground, with 90% of the attraction being underground, beyond the border of the park. So walking past the ride is really just walking past the entrance. In Disneyworld, you have to walk past the entirety of the attraction.
This one sort of goes to Florida. Downtown Disney is enormous and currently undergoing a major overhaul to make it even more relevant. I mean, you can ride a hot air balloon.
But in California, it connects the parks to the hotels. Which means you walk through it every day and there are Disney vendors in the corridor. That means you can buy churros in Downtown Disney.
Which brings me to my next point:
You can buy a churro in every land, every day of the year, in both California parks. In Disneyworld? Fantasyland in the Magic Kingdom sells them, or Mexico in EPCOT. And remember how big the parks are? Yeah. Even if you're in the Magic Kingdom, you're probably really far away from a churro. That's a fail, Disney. FAIL.
Disneyland has all these awesome shortcuts. One to get out of New Orleans Square without having to go through the hub. One to get out of Tomorrowland during fireworks and parades. Plus the train runs all the time, so you can take the train around the park to the front exit, skipping crowds. Also, the monorail runs from Tomorrowland to Downtown Disney, so you can use it to enter and exit the park directly.
Disneyworld has NONE. The train stops running at sunset and the monorail isn't inside the park. Everyone gets herded through the hub and down Main Street. No exceptions.
(Okay, we once got wheeled out the back of the park to an ambulance when my son had a seizure, but that's not really the same)
And this might be the reason I love Disneyland most of all. I mean, a Disney park is a Disney park, and the level of detail is unparalleled, but Disneyland just does it better. Look at this:
That's just on a random post in the railing. And there are little things like this all over the park. In Disneyworld? The rail posts are just rail posts. They're still cleaner than any other amusement park, but they don't have bronze statues on them. Walt didn't have an apartment in Disneyworld (okay, it existed, but he never lived there).
You can't beat the level of personal, intimate details in Disneyland. The park was a labor of love, in a way that none of the others could be, because it was the only one Walt saw to completion.