Two cabinets can carry the same bottle count, the same price and the same photograph, and be completely different objects in a room. The differences are in the parts of the listing nobody reads.
Storage or serving decides everything else
A storage cabinet holds one steady temperature in the 10 to 15 C band and is opened rarely. A serving cabinet holds whites cool and reds cellar-cool and is opened daily. They ask different things of the machine, and a cabinet bought for one job rarely does the other well.
If you want both, that is what dual zones are for, and the temperature guide covers how to set them. If you only want storage, one zone that never moves is the better and cheaper answer.
Compressor or thermoelectric
Thermoelectric cabinets are quiet and vibration-free, but they can only pull the temperature down so far below the room they stand in, which makes them unreliable in a warm kitchen or a summer conservatory. Compressor cabinets cool properly in a warm room and cost less per bottle, at the price of a cycle of noise and a little vibration.
The deciding question is the room, not the cabinet. Measure the temperature where it will actually stand, in the warmest week you get, and buy for that number rather than for a showroom.
The three things the spec sheet hides
Noise, in a room you sit in. A cabinet rated at 40 decibels in a lab is a presence in a quiet living room at eleven at night. Vibration, which matters for long-term storage and is the main argument for thermoelectric or for a well-isolated compressor. And where the heat goes: most cabinets vent from the front or the back, and one that vents backwards cannot be built into a run of kitchen cabinets without cooking itself.
Job: storage / serving / both: Room temperature where it will stand, warmest week: Compressor or thermoelectric: Zones and their ranges: Noise rating, and the room it stands in: Venting: front / back / sides: Space needed including door swing: Shelf type and whether shelves are removable: Bottles it holds in my shapes, not the catalog number: Warranty and who services it:
Shelves matter more than the headline number
The advertised capacity assumes identical standard bottles laid in a particular pattern. Removable shelves, adjustable spacing and at least one deep shelf are what let a real collection fit, because real collections contain Burgundy shoulders, magnums and sparkling bottles. The capacity guide covers turning the catalog number into a working number before you buy.
Look at the shelf material too. Wire shelves are light and cheap, wooden shelves are quieter and kinder to labels, and either is better than a fixed molding you cannot rearrange.
Placement, doors and glass
Measure the door swing as well as the box. A cabinet that cannot open fully against a wall loses you the top shelf permanently. Check whether the door is reversible if the only place it fits opens the wrong way.
Glass doors look better and let light in, which is the one thing wine reliably dislikes, so look for UV-treated glass or accept that the cabinet belongs somewhere dim. And plan for failure before it happens: a cabinet is a machine, and the failure guide covers what to do the day it stops.