Both of these are monthly. Both mean you stop asking what a call will cost. They answer different questions, and buying the wrong one is a quiet waste rather than an obvious one.
A support retainer buys hours and a clock
You get a set number of hours a month, a defined coverage window, and a response commitment that varies by how badly something is broken. Business-down gets a tighter clock than a printer nobody urgently needs.
That shape suits a team whose IT problems arrive as requests: someone cannot get into a system, a laptop is behaving oddly, a new starter needs setting up, a report needs writing. The work is varied and the value is having a number to call with a named response time attached.
Hours in a month are for that month. We would rather say so plainly than let anyone discover it in month four.
Per-device support buys watching
Managed device support is priced per device and does something different: monitoring and patching on every machine, whether or not anyone reported anything, plus a helpdesk your staff can call. Endpoint protection and backup are options on top.
That shape suits a fleet — twenty, sixty, two hundred machines where the failure you care about is the one nobody noticed. An unpatched laptop does not raise a ticket. Neither does a disk about to fail.
The per-device rate falls as the fleet grows, and the coverage window is a choice: business hours, extended, or around the clock.
How to tell them apart in practice
Ask what went wrong last quarter.
If the answer is a list of requests from people, you want hours and a response time. If it is "we do not actually know what our machines are doing", you want monitoring. If it is both — a team that raises tickets and a fleet that needs watching — they combine, and plenty of clients run both.
If the answer is "one urgent thing, once", you want neither. Book an on-site visit or a repair and keep your money.
The questions that decide the tier
Who needs to reach you, and when? A coverage window is the honest constraint. Twenty-four-hour cover costs more because it means someone is awake.
How fast does business-down need answering? This is the number most worth arguing about, and the one we commit to per priority rather than in general.
How many machines, and do they leave the building? Remote and hybrid fleets are the ones where monitoring earns its keep.
The plans page lists what each tier includes — hours, window and response target — and the configurator prices the per-device option against your actual count. Both show the monthly figure with tax on it, because that is what will arrive on the invoice.