@marcel, last night one of my websites was hit 62 times in a couple of hours in an obviously concerted attack, some of the hits were simultaneous, three of them in one second, but so far it has withstood everything that these losers have thrown at it with no problems at all.
At the moment I am using the free version of Bulletproof Security along with the free version of Wordfence and they both ‘play nice’ together and between them they block just about every type of attack. But I will definitely be upgrading to the premium version of BPS this week on ALL my websites, both my own, and my client’s, that is how impressed I am with BPS in particlular — it hides the normally vulnerable files and folders that the hackers use to gain access through the ‘back door’, and Wordfence blocks the ‘front door’.
I highly recommend the combination, and can assure you that BPS does NOT “break WordPress”!