Selection is treated as the pleasant end of a bathroom. It contains one genuinely irreversible decision, and it is not the one anyone deliberates over. The visible trim on a shower — plate, handle, head — can be swapped in an afternoon. The valve body behind it is buried in the tile, and trim does not cross between manufacturers, so the body fitted at rough-in commits the wall to one range for as long as the tile lasts.
The body carries the decisions the trim only expresses. Whether the valve is pressure-balanced or thermostatic, how many outlets it has, and whether a hand shower can be added later are all settled inside the wall. So is depth: a body set too deep for the finished tile thickness leaves trim that will not reach, which is why the tile has to be known before the body is fixed.
Finish durability in a wet room is not what showroom names suggest. Chrome stays the most robust and the least fashionable. Matte black is sold in two entirely different constructions — a hard vapour-deposited coating, and a paint or powder finish of the same colour — and only the first survives being cleaned. The second chips at the aerator and around the handle base. Living brass is meant to change, and is a poor choice for anyone who does not want it to.
Water shows on some finishes and not others, and a current test beats an assumption in either direction. Scale is most visible on polished chrome and on dark matte; brushed finishes forgive it. Untreated shower glass etches permanently where hard water dries on it, which is a coating specified at order time rather than a cleaning problem to solve afterwards.