Bars with backsweep are easier on my wrists and are more forgiving on harsh landings...i still like runing strait bars and am running Lucky NW bars right now.
I like both depending on the width of the bars. if the bars are say 18 wide then backsweep would be pretty useless. I was running phoenix suicide bars recently and i loved the backsweep. they were 20 wide with i think 3 or 5 degrees? i'm currently running Proto baby slayers light and i love them. but it would be really nice if they had backsweep.
It's all preference. I read somewhere that back sweep gives more control. Also, in my opinion they help with tuck no's and front scooter flips. And maybe whips alittle. So ya