Your subscription provides credentials. The player decides what using them actually feels like — how fast it opens, whether the guide works, whether finding a film takes five seconds or two minutes. It is worth a little thought rather than installing the first result.
Start with what your platform offers
The choice is made for you more than you might expect. Android TV and Google TV have the widest selection by a distance. Fire TV has a reasonable set in the Amazon Appstore plus the option to sideload. Apple TV has fewer but generally well-maintained apps. Samsung and LG televisions have the narrowest choice, limited to what is published for Tizen or webOS.
Search your device’s own app store first and pick from what is actually there. Chasing a specific name you read about elsewhere, only to find it was never published for your platform, is a common waste of an evening.
The features that matter day to day
Xtream Codes support. If you use the on-demand library at all, this is the single biggest difference. It is what gives you posters, descriptions and properly grouped series instead of a flat list of filenames.
Favourites. Non-negotiable. Nobody scrolls thousands of channels twice, and a player without a favourites list becomes exhausting within a week.
Decoder options. On Android, the ability to switch between hardware and software decoding per stream is the difference between a channel that works and one that shows a black screen.
EPG handling. Look for a player that can refresh the guide manually and limit how many days it stores, which keeps memory use sane on cheap hardware.
A sensible remote layout. Harder to judge before installing, but a player designed for a five-button remote is a different thing from a phone app stretched onto a television. If the interface requires precise pointing, it will annoy you every evening.
Catch-up, if your subscription has it. Only useful if both the player and the service support it, so check the player before assuming the feature is missing from your subscription.
Warning signs
Be wary of a player that asks for permissions unrelated to playback, one that has not been updated in a couple of years, or one distributed only as a file from a forum post rather than through any app store. Also be wary of any app that arrives bundled with a channel list you did not pay for — a player should be an empty vessel that your credentials fill.
Free, paid and the middle ground
Many good players are free with advertising in the interface, and a one-off payment typically removes it. Some are paid outright. Spending a few dollars once on an app you will use every day is usually money well spent, but install the free version first and confirm it works with your subscription before paying.
Test on a phone first
Whatever platform you intend to watch on, install a player on your phone first and get the credentials working there. It takes two minutes with a real keyboard and it proves the subscription is fine. Then, if the television app misbehaves, you already know the problem is the app rather than the account — which is most of the diagnosis done before you start.