The choice is mostly settled by geography before you ever make it. Punjab has clay, kilns and masons who have laid brick for generations; awal bricks in Lahore have been running around Rs 15,000 to 19,000 a thousand. Karachi's market runs on concrete blocks — a 16-inch solid block costs Rs 60 to 100 and replaces roughly nine bricks of wall at a time.
Where brick wins
Thermal mass, mainly. A 9-inch fired-clay wall rides Punjab's heat swings better, holds plaster beautifully, forgives mediocre mortar work, and takes nails, chases and alterations without complaint. Load-bearing brick construction also lets a 5 or 7 marla house skip much of the RCC frame — that is why the steel thumb rule for load-bearing sits near 2.25 kg per square foot against 4 or more for a frame. The cost is weight and speed: brick walls rise slower and want more labour per square foot.
Where block wins
Speed and straightness. Block walls go up two to three times faster with fewer mortar joints, which is exactly what you want when labour is the expensive line. Hollow blocks take reinforcement neatly — useful in Karachi's seismic detailing — and the flat faces save plaster thickness. The trade-offs: blocks crack telegraphically if the mix was weak, they hold heat differently (Karachi's sea air cares less), and fixing anything heavy to a hollow block wall needs planning.
The honest answer: in Punjab, brick unless your engineer argues otherwise; in Karachi, block and don't overthink it. In the estimator you can flip the grey-structure tier and see the material lines move — the decision costs less than people assume, and the labour market where you build matters more than the material itself.