I always think for the size of their city, and that they have the pull as the big club in West Yorkshire, plus they pull in from North Yorks, and parts of East and South Yorks, that they flatter to deceive as a genuinely big club. Elland Road as a ground is no great shakes and never has been and prior to the Revie era they didn't particular have much history. Post Revie, they've spent 23 years at least outside the top flight, and 3 of those in the third tier.
If football history had turned out different and Sheffield would have only had one professional team it's likely that team would have been a big hitter alongside the likes of Man U and Liverpool.
Sheffield = football city, Leeds = rugby city.