I dont think there will be a "considerable" difference. A few horsepower maybe, The difference between 320 and 330hp perhaps but certainly not anything like 10%.
It'll also allow you to run it on 95octane fuel if you so desire. Might sound **** to most of us, but some folk live in places where super unleaded simply isnt available easily.
What it will do for sure is make the car fell less willing when driven off boost, which obviously isnt great.
All i'm saying is that yes, its annoying, and yes, dont do it if your planning a build, but in this case its done now, so just get on with it and ignore. Its not going to make a huge difference to the figures at the end of the day, and theres ****** all to be gained from dwelling on it.