I played EQ1 for 5 years (and still technically play it, just have been engrossed with EQ2 recently) and in EQ1 I preferred the layout like you do, 3D render full screen for maximum visiblility with windows obscuring as little as possible. I was also a UI modder and it was really ahrd to figure out what people wanted; I apparently never figured that out seeing as my complete UI didn't have a particularly large following (
screenshot).
With EQ2, I don't consider the whole screen my viewing area. I have the resolution way higher than I did for EQ1 and only consider about 1/4 of the screen in the middle of my monitor to be the viewing area I care about, UI bits can litter the edges of my screen. I use the letterbox both because I don't care what's at the top and bottom edges of my view (if I need to see, I simply pageup/down to look and I'm a tallest height troll so I'm just looking down 90% of the time) and also because it blurs textures a little, which I like (I prefer blur and smoothing to crisp lines and edges).
I don't know why my perception underwent this change, maybe others are like me and I like them, where we don't consider everything in the possible field of view to really matter, only what we're looking right at.
Also I play in first person (camera) rather than third person.
Quib