I have broken 10 alu booms in nine years
The brands that were the fastest to break were NP matrix and Pro Limit (broke within a seasons use).
Surprisingly my cheap YES booms lasted quite long (but the boom head was shitty and soft).
I have now bought a Maui Sails alu boom (200 - 250 cm.)
Actually it seems to be quite good value for the money. The boom head is superior to other brands (it doesn't flex and it fits really tight to the mast) and the boom is surprisingly stiff from being alu.
Carbon is stiffer but a hell lot of more$$$$