my thoughts
I think you need to do some of both kinds of workouts to get what you want. To have definition, you have to have muscle built and you also need to have bodyfat down a bit too. I like to alternate MIS with the PS series and on some weeks, I will throw in a tape like Strength, Balance and Flexibility or just do lots of pushups etc, for endurance.
My idea of bulk is not what some others have either. For me, my arms were the easiest thing to get and they are very defined and muscular. Some of my friends think I am too muscular while others compliment me, so really, it is a matter of what you like and want. I build muscle quite easily and that is probably a lot to do with genetics.
I think you will have to experiment a bit and see what works for you. Try 6 - 8 weeks of PS series and then the same with MIS possibly. A lot of people have had great results with the Firm too, however, I do not own even one Firm tape so I cannot comment there.
Hope this helps a bit. To me, cut and defined muscles never look bulky and most women, unless they are taking steroids, can't get that big. To me, bulky is the big women bodybuilders and awesome and cut is Cathe in PS and MIS. But for others, Cathe's look might be too much so it is really a matter of preference.
Am I making any sense to you? Hope so.
Kim