I agree that the slighter larger L01/L02 would be better (note that the large size comes in two different bar spacings - the L11/L12 is too wide)
I have the L02 for my canary.
This design is really fantastic at minimising the mess around cages.
It has horizontal bars.
It allows the owner to access food dishes (and paper floor lining if no grate) with minimal intrusion, if needed for e.g. a scared or very territorial bird.
I like the single/double door idea.
It's worth noting that the measurements stated are the maximums I.e. The base is larger than the barred area. Measuring my L02, the barred area is actually only 13.5" wide x 27.5" long!!!
No pull out tray - The cage needs to be lifted off the base. I don't use the grate. I have multiple layers of paper on the base, and remove the top layer each day via the seed dish drawer. I only detach the base every fortnight for a proper clean and to renew the paper stack. That's easy to do but I'd expect it to be a nuisance to do daily, as you'd need space at the side of the cage to put down the top part whilst you deal with the base.
If you don't like plastic food dishes, then due to the slot in design, you will struggle to find other dishes that would fit in that same place - if you place dishes higher, then the mess containment may be less effective. I use the cage dishes for dry seeds but higher stainless steel ones for wet/fresh foods.
My two budgies, have a single flight cage, I usually have bits of food & feathers scattered around it, even with a vacuum twice a day
, but I personally feel that they're happier with that extra space. That being said, I know that a number of members are very happy with the vision cage.