It was a two part question. I answered part 1 "why so many sets?". People saying "use this set" without some reasoning aren't helping. For instance "this set is great if you prefer a lot of passing and have trouble running" etc etc.
Perhaps "style" isn't the right word, but the point is people have varying abilities, as well as preferences. The slider sets I see here vary wildly.
I use my own set
http://www.operationsports.com/forum...lider-set.html which gives the CPU some teeth. But I've seen harder sets. It's geared toward my own strengths and weakness (good runner, average passer, bend but don't break style defense) plus testing with an online dynasty for the last few weeks. As with all the sets here, you might love it, you might hate it. You might be 10x better than me and find it too easy or dislike how the CPU can light you up if you're not a careful defender.