Kelly –
I am using the 131:1 now so that I can have my Z axis move faster. I have 2 of these Maslow setups that I use, one is fully stock and the other is mostly upgraded. Basically, I have one to test and play with. I went with the 131:1 so that I could move faster since I have a different style of Z axis, I made a Gantry type of setup.
Link to my post about it.
In the pictures you will actually see the stock motor, this worked totally fine with my setup. However, since I have very little friction to move my router I wanted to get a motor with less gearing hence the 131:1. I will say it took me quite some time to get it perfect as far as movement and steps per revolution. My numbers ended up being insanely different than stock since I had a different lead screw and a different motor. I think my final numbers were somewhere in the range of 32 for pitch and 33,500 for steps/revolution. I think I had to do something strange like this because the software wouldn’t allow me to put the steps as high as I would have liked (I think I tried 70,000+ and it balked at me)
I think it depends what type of router you are going to use and what type of Z axis, if you are wanting stock style then I would suggest the stock motor that has more torque. I believe that others have used the 131:1 motor with the stock setup, however, I think that they then started to have problem with the lead screw wearing out etc. (stock has its own set of problems) If you want a modified Z then go with the 131:1 but just know you will have a little more setup on the front end to get things moving the proper distances.
Finally, sorry that this is so far off topic from the original post, oops, maybe this should be somewhere else?