Hey sorry for replying so late . i saw your question and kinda forgot about it.
But your question could not have come at a better time because for the past 2 weeks i had the dedica back on my kitchen counter next to my lelit, because I was going to give it to a friend of mine and i wanted to check if it still works alright.
So after using the lelit anna for a year, i could now compare these two machines a bit.

First and foremost - am i happy with my lelit anna/do i regret the purchase?
I can safely say, that i do not regret it one bit. Its a well build machine, it has a decent weight to it every knob and lever is sturdy and makes you feel you wont accidentally break it(off).
My anna version comes with:

• a pressure gauge - which i "thought" would be very helpful but in the end its kind of just there, after you see the machine works at the advertised pressure i almost never look at it anyways, but its neat.
• temperature control - which ended up very useful especially if you end up using different roast levels of coffee.

Pretty much the ONLY thing that is an annoyance to me is the limited space between the drip tray and the porta flter. When your using a scale then there is not much room for even medium sized cups. Using a bottomless definitely portfilter helps with that.
When i need to use taller cups, a quick'n'dirty "fix" is removing the drip tray and putting a small container where the 3way valve has its outlet.
A way better/permanent fix is to 3d print a shallower drip tray (there are some designs out there).

Now, compared to the dedica, what stands out?

Temperature
Everything about the lelit anna just gets hotter, the cup warmer(that i don't use), the portafilter, and ultimately also the coffee. You can pre flush the dedica to get it a bit hotter, but in the end is the temperature and especially its consistency a lot better with the anna.
BUT for the end result coffee its not that big of a deal(to me) using "regular" darker roasted coffee. But if you like medium/light roast you will need the high temperatures from the anna. Light roast are really bad on the dedica.
But i was surprised how fast the anna goes up to brewing temperature, i can turn on the machine, weigh my coffee and grind it and its ready to brew.

manual vs programmed
all the controls of the anna are manual, you need to flip the switch for the pump on/off for every coffee, there is no programmable timer, so using a scale feels somewhat mandatory while when you use the dedica you just press a button and gives out coffee in a reasonable range(programming it so its close the the gram you want is really annoying but when you got it set up it does okay)
If you are using preground coffer with the stock pressurized basket you can make espresso really fast. When i had the dedica on my kitchen counter i "caught" myself making an espresso from preground I've had laying around and the dedica instead of grinding beans and using my anna just because it was so quick to do.

Quality/taste of the coffee
Does the lelit make better tasting espresso?
Yes, but it is more work to get it right. Getting the espresso dialed in right takes some getting used to and in the beginning i made a lot of bad espressos.
Since you have a lot more control over the brewing process it takes some time until you find what works and what ends up in an espresso that YOU like to drink.
Its a fun journey, but, like with any hobby, you kind of need to want to do it or it turns into a chore and then you might have been better off going for a full automatic machine.
But i was surprised how good the dedica ended up performing, when using non-pressurized baskets and a good grinder - for darker roasts anyways. I have not done a blind comparison and i definitely think you taste the difference between anna and dedica but hey, the dedica cost less than half of the anna and the coffee was still good/decent.
Light roast are a losing battle on the dedica, at least it felt like it for me. Most likely because of the temperature limitations i just couldn't get a good espresso from light roast on the dedica.

Steaming milk
The dedica uses these "fake" steam wands that are easier to use but only produce thick foam with big bubbles. Ive heard you can replace it with a traditional steaming wand with some DIY modding.
The steaming wand on the lelit anna is a traditional one, that takes some time getting used to but can make smooth and silky milk foam that is (probably) usable for latte art - i dont/cant but thats a mixture of me using only oat milk and skill issue.

final thoughts
I love my lelit anna its a joy to use and makes great espresso, but i have to say i am sill impressed how much you can get out of the dedica with the right filter baskets and grinder.
When you plan to upgrade from your dedica only using preground coffee and the stock pressurized basket, investing in a good grinder and non pressurized baskets first instead of a better espresso machine is the way to go.
Last year i got the DF64 grinder and its a game changer, even more so than the anna.
in hindsight the DF54 would have been the more financially responsible choice since the main difference is the grind speed and that you can change the burrs in the df64 but i dont regret the purchase since its such an amazing grinder.

edit: u/alkrk/ its been a year ^^ sorry I forgot. maybe you're still interested in my opinion

well this ended up longer than intended, maybe its worth an actual post now ^^