External water repellents for masonry. How good are they?

I have been asked on numerous occasions how effective external water repellents are for masonry so I carried out an experiment on my garden wall and the result is very impressive.
I have trialed several different water repellents and there was one stand out product that out performed the competition although I have to add that I have not trailed every available product that is on the market.
External water repellents can be an effective resource when dealing with rainwater penetration through porous masonry.

[@isctony]

So the question is, is the product breathable, does it allow moisture out of the brickwork because if the top of the brick there isn't treated, is there a potential for water to soak in to the wall but not be able to escape the wall due to the waterproof coating?

[@goawakeneveryone4365]

Yeah it does breath and it is just spray silicone.