Playing against equals or people who are better?

I've recently been seeing a lot of people saying that a good way to improve is by playing against people who are better than you, which I can understand. Do you think it's more beneficial to play against people who are about as good as you or against people who are better than you? I've heard people say that playing against people who are about equally as good as you is very important for improving.

A mix of the two is best.

Play against people who are a good deal better than you but not against grandmasters

Pointless if they are so superior that you don't understand where you went wrong.

yep

I heard that playing against people up to 200 pts stronger is good for improvement. I normally set my challenges to -25/+200 and play in that range.

@MarkGrubb has it right right.  The ideal opponent is about 200 Elo points stronger than you.  You'll lose a lot, but you'll understand why.  If the gap is much bigger than that, you won't learn much.

Puzzles help you learn how to play better as well. The puzzle will show you how to play better and why your moves are inferior or just bad.

Just make sure you calculate the solution before you make your first move. This will make you a better chess player as well. 

Honestly this may sound counter intuitive but playing against worse players actually highlights your major weaknesses. You will become a more solid player but you won't necessarily become a better player. If you want to really take your game to the next level you need to LOSE to better players.

Most important is to analyze each game. Even after a win. It gives really good insights