If any of these airlines involves having to connect to another flight, don’t pick that airline. Choose from those that have direct flights to your destination.
I am familiar with Delta’s Comfort. I am flying that to Milan in October. You get about 3 inches more legroom, you board before the main cabin, & you are toward the front of the aircraft which makes deboarding quicker.
The seats are the exact same seats as the main cabin. Same recline too. The food is exactly the same as the main cabin. You’ll be using the same lavatories as the main cabin.
Delta has a product called Premium Select which has a little wider and more comfortable seats, better recline, more legroom, bigger TV screens, a separate menu, & is even closer to the front of the aircraft for quicker deboarding. You will also board before Delta Comfort and the main cabin.
The Premium Select seats do not have access to a separate lavatory. You’ll be using the same lavatory as the main cabin. Premium Select is Delta’s attempt at “premium economy” but it falls short to what premium economy is especially compared with some foreign airlines.