Discussions of the relative technical merits of various transformers abound, but I have never seen a discussion of their looks. It is easy to dismiss the appearance as irrelevant in an operating environment, but some folks try to capture a particular feel when building control panels and selecting components for it.
To kick off the discussion, I'll record some of my own impressions and probably gore a few oxen in the process 
First, I dislike the appearance of the venerable--and venerated--ZW (and VW). I know that that shape screams Postwar Lionel to many folks, but I'd hide it if I had to use it. I much prefer the looks of the KW. It says "train" to me. I am indifferent to the appearance of most other postwar Lionel transformers.
Flyer postwar transformers, on the other hand, generally appeal to me--and I have never owned a postwar Flyer train. The handles--on the 18Bs and 30Bs particularly--also say "train" to me. Even the smaller ones generally have more appeal that their Lionel opposite numbers.
Marx transformers just sort of are. They neither excite nor repel me. The big 1859 is the coolest of the bunch.
Prewar was an interesting period. The various Lionel TrainMaster transformers share a family vibe and look pretty good to me. I especially like the V and Z, unlike their postwar progeny.
But I really like the step transformers, like the B, T, and K along with the rheostats, the 440C and 439 control panels, the separate circuit breakers, and the knife switches and switch controllers all just scream Electrical Equipment, almost a Frankenstein's lab vibe. (Heck, I'd even consider the old wet cells and other apparatus for display purposes: those are genuinely Frankenstein--and just a little dangerous, to boot!)
Prewar Flyer doesn't seem to have as many options, though their step transformers are cool enough. I do like the continuous units that have the Flyer shield on the top plate: they do a good job of maintaining brand awareness 
Modern stuff: It mostly ranges from Blah to WhatTheHeck?? to me. The separate push-buttons remind me of '70s TYCO, and the separate control/power brick units just take up unnecessary space. Command Control apparatus are simply best placed behind or under something and ignored.
So these are my thoughts. What are yours?
