I found the Porter Cable Dovetail Jig model 4212 would not give me consistent results in tightness of joint and alignment of pieces. With a few modifications to eliminate variation, I was able to get consistent results. I keep a dedicated router with the bit installed so that I can set up quickly and make a perfect fitting drawer on first try without any adjustments to the jig or router. Saves a lot of time.
Modifications are explained in this YouTube Video https://youtu.be/hTRCSAM-YTk
I am interested in any other ideas to improve the Porter Cable Dovetail Jig