That's a big drop in size
! Both on living space, and storage space.
I agree with the Mercedes chassis being preferred, for the reasons stated.
I know two people that have the Tripple E sister company Leisure van's Serenity and Unity. Both well built, actually I felt exceptionally built, and both very happy with them. One gent with the Serenity, is traveling solo, and finds the space a bit restrictive on storage, but found the livability for one to be fine. His friends, due to his input, went with the Unity as they are a traveling couple. The bed was bigger, and more storage. And I recall right, the Unity was a bit less expensive then the Serenity (Not positive on that, but think it is so.) One of them has a murphy bed, and a pretty nice sitting area at night, for such a small unit.
I know you said diesel, but I will mention that many owners of the last few years of the Trek, on the Workhorse chassis with 8.1, are very happy with the quality of construction, abundant power, and the living space is comparable to a 32-34' Class A. Small enough to get around like the Mercedes chassis. But also a benefit mentioned by those that moved out of C's and B's is that you are sitting up higher in traffic, and have that large panoramic view windshield.
Best of luck on your decision! My intent was to be sure you knew of these other units, not knocking Winnie's