Bathroom count, water pressure and how your household actually uses hot water matter far more than the badge on the front.
A combi boiler heats water on demand, so there is no cylinder and no loft tank. For a one or two bathroom home with decent mains pressure, it is almost always the right answer: cheaper to install, more efficient, and it frees up a cupboard.
A system boiler stores hot water in a cylinder. That matters the moment two showers might run at once, or when mains pressure into the property is weak. Storage means multiple outlets stay usable simultaneously.
The mistake we see most often is a combi fitted into a four-bedroom, two-bathroom house because it was the cheaper quote. The family then lives with fluctuating shower temperatures for a decade.
Ask any installer for the incoming mains flow rate in litres per minute before they recommend anything. Below roughly 12 litres per minute, a combi will disappoint you regardless of its output rating.
Whichever route you take, insist on a system flush, a magnetic filter and a written heat-loss calculation. Those three things protect the warranty and the efficiency figures you were sold.
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