What makes a proper task chair
Task and operator chairs are built for the person who sits down at nine and gets up at five. Everything about them, from the mechanism to the back shape, exists to make eight hours in the same seat bearable.
What separates a task chair from an ordinary one
Three things: a gas lift that sets seat height to the person rather than the desk, a tilt mechanism that lets the back move as they move, and lumbar support that holds the lower spine in position. A chair missing any of them is a visitor chair with wheels.
Beyond that, the differences are about how much adjustment you are paying for. Seat depth, arm height and back angle can all be adjustable, and each one matters more the more different bodies will use the chair. A hot-desked chair earns its adjustment; a chair with one permanent owner needs less.
Mesh or fabric
The main practical difference is heat. Mesh task chairs such as the Ariel and Baye let air through the back, which matters more than people expect in an office that runs warm or gets afternoon sun.
Fabric task chairs like the Barcelona deluxe give a padded back that many people simply prefer, and they look softer in a room that is not trying to be corporate.
Arms are not a detail
Arms that sit at the wrong height are worse than no arms, because they push the shoulders up or stop the chair pulling under the desk. If a chair will be shared, adjustable arms are worth the difference. If it will not, fixed arms at the right height are fine and cheaper.
When to specify heavy duty instead
Standard task chairs assume one user, one shift. Control rooms, security desks and any 24 hour operation wear them out fast. The heavy duty range uses reinforced frames and stronger gas lifts for those environments, and for heavier users generally.
If the sitting is the problem
No chair fixes sitting still for eight hours. If back trouble is the reason for the purchase, look at ergonomic and posture chairs for more pronounced support, and consider whether a sit-stand desk would do more good than a better chair.