Where there is enough room in the reveal, internally, behind external brickwork, we would always recommend this traditional option with weights & pulleys.

If your reveal is the same dimension inside and outside or if your building is more modern in design, then perhaps a Spring Balanced system is a more suitable option for you. 

This is a cross between a spring balanced sash window and a casement window, as it features both types of opening, which is suitable for Fire Escape requirements as the whole Sash window can open from the inside as a casement does.