This is a matter of personal preference: if you make the notecards yourself, you incorporate the knowledge learned from muscle memory while writing the information on the card. The cards will also have all the knowledge you choose to learn.
If you use a program like Anki to make the notecards yourself, you spend less time creating the notecards. My experience with this though is that when I want to make math flashcards, LaTeX doesn’t integrate very well–thus I’m forced to make cards by hand. If you use an online resource like Quizlet, you spend no time creating the cards and get more study time. But the cards may not be in the most effective format. But still for things like foreign language, Quizlet is incredibly effective–spelling tests, matching games, etc. Helped me get an A! 
Quizlet is the way to go.
Less paper, create your own quizzes, mobile app (test yourself at the bus stop), games, starred lists for most commonly missed.
The best part of quizlet is that you can search existing decks. Sometimes you can avoid making flashcards entirely just by using existing decks already created! 
There is a reasonable amount of research that suggests that retention is higher when using old-fashioned textbooks versus electronic versions. Not sure if that carries over to this exact situation, but it’s something to think about.
I’d recommend paper/“traditional” flashcards. I found that most of my actual retention took place in physically writing out the information on the index card, rather than the actual review of them. Also there’s something to be said about the tactile aspect of it - holding the index card in my hand, up to my face, helps with my memory rather than simply staring at a screen.