It depends upon various factors however most important is the location of your site. For example if you are constructing your house in Karachi or Islamabad, construction method adopted is frame structure (column beam), and both cities have easy availability of blocks (inferior to superior quality). In such a scenario blocks can be used however bricks are and will remain always superior to blocks. Bricks have more strength (around 1800 to 3000+ PSI) as compared to concrete blocks made on site, however branded concrete blocks such as Izhar’s can have a strength up to 2500 PSI. Bricks have a disadvantage of seepage issues whereas concrete blocks do not. Still for residential projects my personal recommendation will be bricks if you are constructing your house around Lahore/Islamabad. For Karachi, availability of bricks is the major issue hence concrete blocks are used there. Same applies for Lahore, where availability of blocks is a major issue hence bricks are mostly used in all type of constructions. Another main factor that should be taken care of is availability of labor for brick or concrete masonry, e.g in Lahore availability of labor for concrete block masonry is difficult, hence using normal brick masonry labor for concrete block masonry can cause defects.
Usage of low quality bricks, ravi sand, incompetent workmanship, neglecting technicalities of damp proofing during foundations stage are the main causes of seepage, i have posted a complete article in blogs section under the heading of “house foundations” explaining all technicalities.