Smart plug vs timer

Both of these turn a light on and off without you. The difference is what has to be working for that to happen.

A timer needs power and nothing else. It keeps its schedule in a house with no internet, no phone and nobody home, and it will still be doing it in ten years. The astronomic type goes further and follows sunset through the year on its own.

A smart plug needs your Wi-Fi, an account, an app and a company that keeps the servers running. In exchange you get control from anywhere, voice, scenes with other devices, and schedules you can change in seconds.

Neither is the smarter purchase in the abstract. What decides it is whether the value is in the schedule or in the control.

1. A porch light that should follow the season: an astronomic timer, or a smart plug with a sunset schedule. Both work; the timer keeps working when the router does not.
2. A lamp you want to switch from bed: smart plug. A timer cannot be asked.
3. Holiday lights: either, outdoor-rated. A countdown timer is the classic answer, and it is hard to beat for the price.
4. Making an empty house look lived in: smart plug if you want to vary it while away; a timer if you want it to keep going regardless.
5. Hardwired fixtures with no plug: an in-wall timer or a smart switch - a plug of any kind is the wrong product. See best smart switches.

Kasa Matter Smart Plug EP25 - the smart plug pick. Matter support means it works with Apple Home, Alexa and Google rather than one app, which is the hedge against the whole category's weakness. Small enough not to block the second outlet.
Cons: it switches rather than dims - dimming stays with the bulb; it is indoor only; and it depends on your Wi-Fi for anything beyond the stored schedule.

Kasa Smart Wi-Fi Outdoor Plug EP40 - for outside. A weather-rated outdoor plug with two independently controlled outlets, which is what string lights and a path fixture on separate schedules actually need.
Cons: the same Wi-Fi dependency; and outdoor plugs want a sensible mounting position out of standing water.

Intermatic ST01K astronomic timer - the timer pick for hardwired lights. An in-wall timer that knows sunrise and sunset for your location, so a porch light follows the season for years with nothing to maintain and nothing to connect.
Cons: it replaces a wall switch, so it is electrical work and not a renter option; on and off events only, no dimming; and changing the schedule means going to the wall.

BN-LINK outdoor photocell timer - the plug-in version. A weather-resistant outdoor timer with a photocell and countdown modes: on at dusk, off after the hours you choose, with no app and no wiring.
Cons: the photocell needs to see the sky, so where you mount it matters; countdown modes are fixed steps rather than a real schedule.

An indoor plug used outdoors. The most common and the most dangerous shortcut in this category. Outdoor-rated products exist and cost very little more.

A smart plug on a lamp with its own switch. If someone turns the lamp off at the lamp, the plug can do nothing. Leave the lamp switched on and control it at the plug.

Expecting a plug to dim. Switching and dimming are different jobs. Dimming comes from the bulb or from a plug-in dimmer.

Putting a timer on a motion light. The two fight each other. Pick the behavior you want - the comparison is in motion sensor vs dusk to dawn.