Anki is by far the most versatile spaced repetition software out there. It's not the easiest one to install and understand exactly how to use, but once you are familiar with it, you can do anything. Has support for media (pictures, video, sound) on flashcards, advanced cloze sentence creation, a very advanced card browser allowing you to select and edit large decks easily. I could go on, but in general, Anki is the best overall flashcard program if you want control over your studying. It's not the quickest or easiest one, but if I had to use only one SRS, it would be Anki. Read my recommendation here.