Yes there is a significant difference between a slip on and a full system with the proper tune. I have an Akrapovic full system for sale in the classifieds if you are interested.
2004 CBR1000RR (Yelena)- modded track/street bike, 398lb RTR!
2002 RC51 (Christina)- rode hard and put away wet, sold
2006 CBR600RR (Nikki) - how the addiction started, sold