Any renowned brand will be good for your engine, since you change it that often. Your oil doesn't have time to deteriorate.
![Laugh :laugh:](https://www.mk5golfgti.co.uk/forum/Smileys/newsmileys/laugh.gif)
Don't see the point of paying an extra if you can buy a cheaper good branded oil. I don't know how much you pay for Castrol, but I'd choose the cheaper.