The stock pipes with free flowing slip ons are going to be hard to beat. Some of the 2 into 2 pipes are just about as good along with some 2 into 1. After market pipes look nice and some will give you some gains but don't expect anything drastic. Mostly they just move the torque curve a little bit.
Billy

 

Cycle Shack Slip Ons
http://www.youtube.com/watch?v=KPeA827uZxk

Rineharts 2 ino 1
http://www.youtube.com/watch?v=gfGjaaeAz7c

No problem with performance with either one.

The stock headers has a crossover pipe that many
after market 2 into 2 full systems do not.

I’ll take stock headers and slip- ons over full
system any day. Same with my Night Train.

 

2-1 systems will give you a slight advantage over 2-2 systems if you are running through the RPM's, if you are just a cruiser you will not really feel any difference. 2-1 having a larger diameter exit will tend to give you a slightly deeper tone, but will certainly come to life when you give her a good twist.
If you want a good solid performance for typical street and little to no mid-range fumble, try the BCT QQ baffles in 2-2 pipes, I had that setup in my BR 2-2 and it really brought those pipes to life.

 

I personally don't have the background in performance mods to have any technical opinion, but I did install an R and B Racing 2 into 1 system on my last Ultra and really did like it. If nothing else the web site is a good read with lots of technical stuff that explains it all. www.rbracing-rsr.com/

 

Same with the Bassani Road Rage 2-1. Quiet enough for coming home late at night, so as not to disturb the neighbors, but barks real nice when you want it to!

 

until i went with 2 into 1 i was seriously thinking about gearing the bike down. 6th gear is much more usable with the new torque curve

 

I got the Samson because I liked the looked - wanted something easy to clean but not too loud with a nice sound. It fills all of those nicely. First one is mine, second one is one Samson did.

http://www.youtube.com/watch?v=KxGwshPusok


http://www.youtube.com/watch?v=9FnMh3-kdlo

 

I do like the look of the Samson!

 

guess I am just old school, just cant get used to the look of the 2into1 look

 

I went from 2 into 1 on my SB to stock headers and slip-ons for that same reason.
http://s1125.photobucket.com/albums/.../Street%20Bob/