I did mean elaborate in size and complexity, not design.
Sheppard West's GO connection is (let's be honest here) only theoretically useful, and there's basically no potential for ridership growth in the industrial units along Chesswood...it's Downsview Park, especially the proposed condo blocks, that will add some riders. Sheppard West may never have more than 10,000 rides a day but that's fine...it's not a competition.
I'm thinking that the York U stop will be larger because ridership will be higher and you'll need that extra space to deal with the crowds and the fire code requirements about the space such a crowd needs. However, stations like Sheppard West clearly should not be built to the same scale as a York U or a Finch.
York U should be a modest station, like Lawrence without the mezzanine layer, or College with a second entrance (I'd suggest something like Wellesley but all stations should have an entrance at each end). York U won't be amongst the most-used stations like Finch because it'll lack feeder buses...students tend to flow in and out of campi steadily all day rather than in compact 9-5 bunches like office workers, so no special designs to accommodate huge crowds should be necessary. Finch is enormous but its size is understandable given the YRT/GO terminal...stations like Leslie are inexcusably overbuilt.
If stations "need" to be the size of an open pit mine because the platforms need to be deep, we should be looking at surface/trench/elevated options instead of obsessing over tunnels (part of this obsession is merely a desire to make subways seem "too expensive" as an excuse for not "giving" one to each ward/municipality/neighbourhood). Leslie should have been a surface/elevated station...if it was higher up, Bayview/Bessarion wouldn't have needed to be so deep (seeing Bayview and Leslie's vast mezzanines lit up with dozens of lights is truly saddening).
This type of "what if we do X and Y and save $50 million?" discussion was totally absent from the Spadina extension and its ridiculous price tag is frequently used to justify eschewing subway construction, whereas an streamlined extension with practical cheapenings could have been used as a model for future frugal and efficient projects. No one actually cares what the subway looks like...some people say "oh, added aesthetic elements only add like 10% to the cost" but virtually all transit users would rather have a 10% larger system. I don't think there's anyone in the entire city who would take the TTC if only every station looked like Downsview. Ideally, people aren't in stations long enough to appreciate their design, anyway; they're swifted away on trains and buses.