I purchased a new Mazda 6 in 2006. when doing my research, I found that the range available in Ireland was different from that in England. In England the range starting with the entry level was:
S, TS, TS2 & Sport
In Ireland there were 3 models available which I seem to remember corresponded to the S, TS & TS2. they are:
Comfort, Touring & Sports Touring
The Executive I believe from memory came in during the final production of the first Mazda 6 model and replaced either the Touring & Sports Touring (or maybe both) So my guess is that the two you refer to will be pretty much the same. The Sports Touring had a few extras over the Touring. A sunroof was the most obvious one.
Being in England I bought a TS2 diesel and I like it that much, I've still got it. 6 years of trouble free motoring.
Sorry the reply is a bit vague, but maybe someone in Ireland will be able to give you a more detailed answer.