The best setup is the one that fits the room's usable space and offers an accessible route for your cat. A tall tower may be simpler to position and maintain, while wall shelves can free floor area where the wall and installation conditions are suitable.
Compare the complete width and depth, including projecting beds, rather than choosing the smallest base automatically. Check doors, windows, heaters and everyday walking routes. Your cat also needs somewhere clear to approach and leave the structure. A high bed with no comfortable way down is not an efficient use of space. Sketch the room and mark the furniture at different heights. Sometimes one well-sized tower is more practical than a complicated wall route, while another room benefits from a few carefully placed shelves instead of a large central structure.
Draw both options on the same room plan: one tower footprint versus the projection of each wall shelf. Shelves save floor contact area, but their usable platforms still occupy room space above it.
For product comparisons alongside this advice, see Feline Sovereign Spire and Modern Vine. The details below explain their sizes and uses.
Further reading: cats.org.uk; cats.org.uk; cats.org.uk.
Feline Sovereign Spire
Modern Vine
SkyRoute wall climbing set