Start from the room, not the datasheet
Most buyers overthink the brand and underthink the environment. A cafe menu board and an airport wayfinding screen are different machines that happen to look alike. Write one sentence before you open a quotation: this screen will show what, to how many people, at which spot.
Size follows viewing distance
Under 2 m: 15.6 to 32 inch. Two to four metres: 43 to 55 inch. Four to seven metres: 65 to 86 inch. Beyond seven metres: 98 inch. Too small and nobody reads the price; too large and it swallows a small wall. A checkout counter is happy with 21.5 to 27 inch, and putting a 43 there just blocks the till.
Brightness follows ambient light
Normal indoor light: 350 nits. Facing a window or a bright lobby: 500 nits. Skip this step and the promotion greys out by noon, which reads as a broken screen rather than a specification error. Direct sunlight outdoors is a different product with a different price — see the outdoor line.
OS: Android first, Windows only when required
Android handles menus, promotions and scheduled loops with no licence cost and no update treadmill. Step up to a Windows OPS when a specific PC application or a locked-down browser is mandatory. Paying for Windows just in case is the most common line item we remove from a quote.
Wall or floor: a mounting decision with a cost
Wall-mounted is cleaner and cheaper for corridors, above counters and in meeting rooms. Floor-standing draws attention at an entrance, needs no drilling into a landlord wall, and can move when the layout changes. Same panel either way; the chassis decides the price.
Content management from day one
Running three screens or more, use a cloud CMS from the start: group them, push playlists, schedule by daypart. One screen on a wall is fine with USB or SD auto-loop and needs no network. The mistake is buying three screens and managing them one at a time for a year.
Touch only where interaction is real
Self-ordering, wayfinding and check-in need touch. Pure advertising does not. Specifying touch on a playback screen adds cost, adds a sheet of glass that can fail, and gives staff one more thing to wipe.
Certificates and duty cycle
For tenders and customs, ask for CE, FCC, RoHS and CCC before the order, and check that the certificate covers the exact model. For 24/7 duty, confirm the industrial board and the ageing process rather than assuming the box is built for it.
The one-page checklist
Distance decides size. Light decides brightness. Task decides operating system. Mounting decides chassis. Screen count decides whether you need a CMS. Settle those five and the rest of the datasheet stops mattering.