So I'm looking at various forward control setups for my bob. I've noticed there's some very expensive units that look like they have the master cylinder on them... The cheaper ones don't. What's the difference and what are the pros and cons here?

 

I have the Harley ones on my bob. I wouldn't know the difference in the other. These are fine for me.

 

The type without the master cylinder includes a longer activation rod that runs from the pedal back to the original m/c. That can cause clearance problems with some pipes, but it's less expensive and a bit easier to install. I have the HD reduced reach on my SB.

On my 82 FXRS I used the type with the m/c because it was all I could find to fit that bike.

 

Personally I prefer the Master Cylinder up front, I think it looks better and I think it is easier to deal with. You need to remount the switch and pick up a new brake line hose, but if you ever make any changes or extend them, it is a simple hose to adjust instead of the rod.
I have tried a few different sets and I am very happy with my new

http://supremelegendsusa.com 2" extended controls.
They are excellent to deal with too, Bill the Owner is a great guy.

They have numerous choices and the quality is top notch.