The "best" is an emotive word.
The cheapest, most stable and best supported hardware in my view is the Raspberry Pi. By a LOOOOOONG way. So that gets my vote.
There are some really simple things you can do to make it a rock solid platform. I've had Pi's running for several years at a time. Only rebooting for the occasional refresh.
Here are my tips:
- Get a decent power supply.
- Connect that power supply to a PC UPS (uninterruptible power supply) or get one of the battery addons for the Pi - though the former is the better option as you can also plug in routers, switches, access points, etc. The Pi doesn't like having power cut off. A UPS will also filter the power which is another device killer so even if you can't afford a UPS, at least get a filtered extension.
- Get a branded SD card of at least 32GB. I always use the Samsung EVO or EVO+ cards. The extra space allows lots of room for "wear levelling" which will mean that the card will last for years even with heavy use.
- You can go further by adding an external disk interface and putting a hard disk or SDD on.
- Clear out the rubbish. If there are packages you don't need, get rid of them.
If you have a newer Pi, you might consider adding "webmin" and configuring it to automatically update your installed packages. Not only will you be able to enable remote admin if you want, you won't have to worry about system updates. You can also use webmin for alerting on things like disk space, services failing, low memory, etc.