I've tried my settings all over the place as far as rate, cl_updaterate, cl_cmdrate and whatnot but have had no visual/performance changes from these settings. At least nothing noticeable.
I keep my settings at 25000, 66, 66 and have no issues either way... That being said my internet speed is optimal and my fps usually is a steady 300 capped. Either way if you're experiencing lag make sure its not graphical first off.
Check your fps at the time of the lag. It could just be that your machine is lagging rather than the server/internet connection.