Not necessarily. Sleep mode is fine for daily use, but a full restart every few days clears out issues that sleep alone doesn't fix.
This question splits people into two camps: those who shut down out of habit from older, slower-booting computers, and those who never turn theirs off at all. Modern hardware makes either approach workable.
What actually changes performance and stability isn't the daily on/off switch, it's how long the computer goes between full restarts.
Sleep keeps your session in memory using a small trickle of power, so the computer wakes in a couple of seconds with everything exactly where you left it. It's not the same as leaving the computer fully running and working overnight.
Sleep mode nightly for convenience, with a full restart every 3-7 days, works well for most people. If a major update asks for a restart, do it that day rather than dismissing it repeatedly.
Power off completely if you won't use the computer for several days or more, during a thunderstorm, before moving a desktop tower, or if a laptop will sit in a hot car or bag for travel.
Desktops left in sleep mode use very little power, often a few watts, so the electricity cost of nightly sleep is minor. Laptops on battery drain more slowly in sleep than while awake, but one left plugged in and asleep for weeks should still get an occasional restart.
You don't need to shut down every night, but don't let a computer run for weeks without a real restart either. A restart every few days covers most of the benefit.
No, sleep mode typically draws only a few watts, far less than active use, so leaving a computer asleep overnight costs very little.
Roughly every 3-7 days for most people, or sooner if it feels slow or an update is waiting to install.
No, modern computers handle frequent power cycles fine, there's no meaningful wear from turning it off nightly.
Yes. Hibernation saves your session to the hard drive and powers off completely, using no battery, but it wakes more slowly than sleep.