I wouldn't say I know best Mitch but having dealt with various things through the years And been fortunate enough to see some of the latest products from companies and respected tuners you can clearly see where some of the older equipment is far from the best available.
As for Julian I'm quite sure He uses SQ6, the T6 is old, 2 decades old now, ahead of its time for sure but it's quite outdated and definitely not what he would supply on a current rally cross engine.
A Syvecs S6 even in its basic form has all the features you require, Life offer different options so yes you need to add on certain features, I'm not sure how the prices compare at that point but essentially they are the same thing, it's only as good as the person using it though, we once had a well known car through the door on a s6, it was controlling 6 coil packs, 6 injectors, boost, cam and crank, nothing else, totally pointless, any ecu can run a engine, some better than others, it's how it actually deals with situations and controls stuff that makes one stand out from the others