I support PARS as a product as well. On balance, a lot of things many people will claim can "only be done in PARS" can in fact be done in SIMS... but it might be that you will end up paying more for them (i.e. adding modules like Lesson Monitor and InTouch to do what PARS will supply in a single product)... or it might be that you get the same functionality but it can be "clunkier" at times.
On the money side, the PARS purchase a couple of years ago was a no-brainer for us. We'd never bought Lesson Monitor, so I quoted up on this and was given a certain figure. When I then went to TASC for a quote on PARS, the figure was more or less exactly the same. Our decision was between a specific module of SIMS that only does so much, versus the same price for a product that does so much more. We went for PARS and haven't looked back, though we did suffer a few mishaps with the Grading features due to opting not to pay for the extra training days.
PARS training as (usually) provided by Ms Urey is exceptional. There is a day rate involved but if you scrimp on it, you'll find productivity and user experience both suffer in the long-term.