Shorty Headers and Alter-K Kit...

I have these now: http://www.summitracing.com/parts/HED-78050/

They're horrible, but I needed something cheap at the time, now that I have money for an upgrade I'm looking at the TTI headers. One question though, I'm no expert on headers...whats the pros/cons between 1 7/8" and 1 3/4" step headers?

Thanks!
Craig