A bit of a late chime-in from Perth Western Australia
I have 2 CVO's , a 2008 CVO springer and a 2013 CVO Breakout
2008 Springer has a TTS dongle , "fitted up" by me , I have used TTS since 2008 on other bikes. I have reccomended TTS to ALL of my riding buddies , as I have been well happy with the results obtained using it. I also do the majority of their tuning for them using my laptop(s). My 2008 CVO Springer runs well
2013 CVO Breakout came to me as a 4000 K's used bike ( 2,500 miles ) and already had an "1800 pro-upgrade kit" installed from brand new at the HD dealer , including an SEPST "Super tuner" dongle. The HD dealer had used a stage 1 cal for 255 cams , and the bike had 259E cams and high comp' pistons etc etc. Bike was a flat as a pancake compared to my Springer CVO. There was no calibration in the SEPST tune file for 259 cams and pistons on a 2013 CVO breakout !
So I had to learn the SEPST routine , having been a TTS long term convert ( not "expert" haha but my mates think I am !)
I find TTS easier to use than SEPST , as a private operator in my home garage.
Also one of my mates had dramas with his 2011 streetglide when he had a 120R motor installed and Mastertune TTS came to his rescue ( via me ) when Steve Cole ( Of TTS !) helped out immensely. We could not have had that help from SEPST in any way or form AS THERE IS NO WAY TO CONTACT ANYONE FOR DIRECT PERSONAL SERVICE AND HELP.
In short I would use TTS all the way , and would have it on my own CVO Breakout had the money already not been spent on an SEPST tuner dongle.
For what it's worth , a reputable indy tuner in the eastern states of Australia emailed me a cal from a 2013 CVO Breakout with " 1800 pro-upgrade" kit that he had TUNED WITH A SUPERTUNER and now the Beakout flies indeed