Prioritise the features that will make the furniture practical in your household. Removable covers can be valuable when your cat sheds heavily, tracks dirt or frequently rests on the same cushion, but check whether they are actually washable and easy to refit.
An elaborate shape may still be manageable if its surfaces are accessible and the care instructions suit your routine. Compare the likely cleaning work honestly rather than assuming you will maintain a complicated design differently once it arrives. Also consider the availability of replacement covers and how securely they attach. If two products meet the same size and support needs, easier maintenance may provide more lasting value than extra decoration. You do not have to choose the plainest option; choose a design whose appearance and care requirements you are comfortable living with over time.
Time the routine you would realistically repeat: removing a cover, washing it, drying it fully and refitting it. A spare compatible cover may make that routine easier, but only count it as an option if it is actually available.
For product comparisons alongside this advice, see Linden wooden cat tower and Arbor Retreat. The details below explain their sizes and uses.
Further reading: cats.org.uk.
Linden wooden cat tower
Arbor Retreat
Floral Canopy