Retul vs F.I.S.T Fitting options

These two things aren't comparable. It is like trying to convert pounds to decibels. Different things.

Retul is a motion capture/video analysis technology that is adapted/developed for analyzing bike fit and position. In the right hands it is especially good at revealing opportunities to improve pedalling efficiency and identifying factors during the pedal stroke that may contribute to discomfort and reduce efficiency.

F.I.S.T. or the Fit Institute of Slowtwitch is Dan Empfield's school on triathlon specific and now, road bike fit and positioning. Empfield invented the triathlon bike as we know it today, along with the stack and reach method of measuring and equalizing bike dimensions and fit data.

F.I.S.T. teaches fitters where a rider needs to be on a bike, how they should be positioned in compliance with the ideas behind the design of the first triathlon bikes and how to practically select the optimal bike based on X and Y coordinates in the real world. It is the single most useful set of fit protocols in the industry.

Ideally, a F.I.S.T. Certified fitter would be using a motion capture technology like Retul. Retul is the "tool" and F.I.S.T. is the "know-how".

If you had to make a choice between the two, Retul is only as good as the person using it. F.I.S.T. trains to a universal standard of competency in triathlon (and now) road bike fit. If a fitter is current and proficient in their F.I.S.T. methodology it means they are a competent fitter. Even a great moton capture system like Retul doesn't make an inexperienced fitter an experienced one.

All depends on the individual fitter and how well 1. you communicate what you want (ie priorities) and 2. how well he interprets what you are saying. 

Fits are dynamic and based on feedback from the rider. It's not like they put you on the bike, take measurements and say, BOOM, you are "fit" perfect. They take all kinds of things into consideration and then add in their "expertise"...this is where the fits will diverge from fitter to fitter.....no matter what system they use.

That's why most riders fits change over time as they first learn what they like and then make adjustments as they go.