There's no fixed rule here, you can experiment and try different movie codecs (compression) to see what works best for your machine. We recommend using Photo-Jpeg Quicktime movie compression at 1280 x 720 resolution.
Why Photo-Jpeg? Because it is a very low CPU intensive codec yet retains image quality very well. If your video duration is longer than 1 minute, then please try converting to H264 codec for smaller file size.