Cant really compare much from personal experience, but from what Jim has said of his experience shorts stories and Novelettes tend to take nearly as much time and effort as a full novel does, but with less overall return on it. If it were me, and I didnt have a particular deadline or publication restriction involved, Id probably say go ahead and shoot for a full length novel. It doesnt have to be a King/Jordan size brick to still work, and as you say the shorts arent really being consumed as much these days. However, if what you have in mind fits nicely into a shorter format, I would not recommend adding unnecessary bloat just to try to inflate the page count.
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