More acts seem to choose the First Direct Arena over whatever Sheffield Arena is called these days. It's a fact, just look at the listings in the papers on a Friday. Some do both but rarely do you see Sheffield without a Leeds gig as well.
Can't just be because it's newer. I actually disagree with Owling, First Direct is too big - the artist is like an ant on stage if you're nowhere near the front, good job for the big screens behind. There's no parking close by (well there is, but because of the loop and traffic lights, it takes 2 hours to exit after a concert - I know, I asked) and the one-way loop makes it hard work to get dropped off and so it's boom time for the taxi companies.
The City council probably does a better job of promoting Leeds I guess, perhaps they'd have made more of being the home of football if the oldest club in the world was Leeds FC. Sheffield just looks and feels tired right now and there's absolutely no inspiration to want to venture into the centre anymore except to go to the City Hall - an oasis in the middle of shiteness