They are not mutually exclusive. AVI, MOV, Flash, MKV and others are actually wrapper formats. They can contain MPEG video within them. It doesn't matter what format she uses, any of those are fine. But Leo does recommend using a compression, or CoDec (Compression/Decompression) called H.264. That will give the best quality while still maintaining a smaller file size. It's also rapidly becoming a standard.
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