I feel the SCT is the best flash tuner for a few reasons , it wont change your stock factory strategy to what the tuner wants , it datalogs , the new SCT cloud tuning is in beta test where you can down load your tune directly to the flasher vs downloading it to your PC then to the flasher
I also feel I have the best tune files for the MK3 Focus and you get a full custom tune vs canned tuning
SCT is the best choice. Within that you have options. Tom is very reputable and creates custom tunes. You also have injected engineering which also has good reviews. Mike at RDC is in the process of coming out with a tune. Lastly you always have the option of going local, There are some really good tuners out there that do service locally and can offer either canned tunes or custom, plus they can normally dyno your car at the same time which is always awesome. It really comes down to how much you want to pay and doing your research on the forums here to decide which one fits what you want to do the best. There is an abundant amount of info here on the forums don't be afraid to use the search bar and spend some time researching, in the end it will only benefit you.