No, you certainly are not alone in your appreciation for the finer aspects of design. The Steampunk deck wasn't really my cup of tea, but hey. To each is own. I'm sure someone liked it. I feel like Theory 11 tries to emulate the "Classy, luxury" feel and Ellusionist tries to emphasize the magical elements in all of their products. Theory 11 probably appeals to most flourishers due to some of the reasons that ChristopherT mentioned before me. But each site has their own small collection of jewels that make them each stand out. Ellusionist, for me at least, completely kickstarted this whole custom deck arms-race. They have the Ghost decks, the Black Tiger decks, Arcane decks, Shadow masters, Masters decks, I liked all of those.
But in recent times, it appears to me that Ellusionist is taking efforts to try and emulate some of the elements Theory 11 uses with their products. The minimalist designs (LTD), the infinitely less "magical" feel (Executive, Fathom??) and consider that you haven't seen a "gaff" deck from Ellusionist in years. That used to be a big thing for them, but they seem to have completely moved their focus away from another element of magic. I'm also not fond of this rather glamorized focus on gambling (Artifice, Madison's...everything). However, the Artifice decks are awesome. I love the clean cut look of the bordered blue and green decks, the Madison decks have settled nicely with the community as well.
Like any business, Theory 11 has its flops and it has its triumphs. Flops, I wasn't a fan of the Steampunks, the Archangels, the Charity Waters and the Animal Kingdoms. However, the Monarchs, the Sentinels, the Centurions and the Guardians are great decks.
So to each his own, I prefer Theory 11 largely because of the community, the customer service, the Wire and the cardistry. I can acknowledge why one would be attracted to Ellusionist, but Theory 11 feels a bit more personal.