The resale argument, honestly
Estate agents generally advise keeping at least one bath in a family home, because buyers with young children filter for it. In a one- or two-bedroom flat, or a property aimed at professional or older buyers, a large walk-in shower usually presents better than a cramped bath nobody uses.
The practical rule: if the property has two or more bathrooms, converting the second one to a shower room is low-risk. If it is the only bathroom in a three-bedroom house, think twice.
Room size and the 700mm problem
A bath needs 1700×700mm plus access. A comfortable walk-in shower needs 1200×900mm plus a dry zone for towelling. In rooms under about 2.2m long, the bath usually wins on floor efficiency because you can shower over it; in wider, shorter rooms the shower wins because a bath would block the door swing.
Drainage and the bit people forget
A shower tray or wet-room former needs a gravity fall to the waste. Where a bath sits on a suspended floor, there is usually depth to work with. On a solid concrete floor, achieving that fall can mean a raised tray, a slim-line former, or a pumped waste, each of which changes cost and step height. This is decided at survey, not at the tile shop.
Doing both without ruining the room
In many family bathrooms the best answer is a shower over a straight or P-shaped bath with a proper hinged screen, rather than a curtain. It keeps the resale bath, gives a usable daily shower, and costs far less than splitting the room into two zones. The compromise is showering comfort, which a wider P-shape and a good screen largely solves.