I have both. I am one of the rare ones who doesn't particularly care for the Stripology ruler; I still prefer my June Tailor. I find the Stripology unnecessarily large and bulky. It is made out of hard plastic whereas the JT is made of softer plastic. I thought I would like the hard plastic better, but I don't.
I have several JT's in different sizes. The biggest one (the Pro) is really suitable only if you plan on cutting lots of 2.5" or 5" strips. It is very large and I guess I just don't like the large versions of these mats. They just feel awkward to me.
My preference for backing the JT's so they don't slip are the adhesive Grip Strips, which can be cut to size and placed anywhere underneath the mat. These stabilize the JT's for me so they don't slip. Here is a link to what I use on Amazon:
http://www.amazon.com/Guidelines4qui...dp/B009DF9DLA/ .
I have not had a problem with nicks in the plastic from cutting. I think it really depends on your cutting style. If you always make sure that you are positioning the blade in an upright position as you cut, which is what I do, you won't get nicks. My guess is that nicks come when you are not paying attention and allow the cutter to be cutting at an angle.