How do you propose a car with 40bhp (or 20%) less power than another identical car is going to be faster? Yes a DSG will change gears faster to the tune of 2/10ths of a second per gear at the absolute most. There is one gear change required from 0-60mph. The cupra is one full second faster to 60 than an FR. Take the 2/10ths of a second off the second slower time and hey presto, still 8/10ths of a second slower. On the off chance you need two changes, you are still 6/10ths of a second slower.
Now try 0-100mph. This needs 3 changes. Is there 6/10ths of a second difference between a Cupra and FR from 0-100mph? No. You are now even further ahead in the Cupra.
You are right about this not being what the original post was about, but had to say something when I saw someone say that they though a standard FR TFSi DSG would be as fast or faster than standard Cupra. In two words, no chance.
To be honest, even if the DSG box was available in the Cupra I would not have it as it is not my cup of tea. Yes I have driven a DSG, but as much as people want to say they can drive it in manual mode, it still changes up at high rpm for you and it still changes down if you go too slow.
For the amount of money DSG costs on an FR TFSi, you are looking Cupra money pretty much and with it superior brakes, uprated engine, bigger turbo etc etc but more importantly more power and no less mpg. Fair enough if you want or need an automatic, but dont kid yourself that the less powerful car is as fast or faster despite the magic gearbox. The Cupra would still be faster in accelaration and have a higher top speed than an FR DSG. Remap the FR, and that would most likely no longer be the case, but a standard Cupra would not be miles behind it