Both seem very low to me for
huffyuv lossless files. Standard DV is 25Mbit/s which comes out to 13GB per hour (with audio stream also in there) and being that lossless files typically take up 30GB per hour, the bitrate should really be more like at least 60Mbit/s for the video stream part. Usually most people don't focus on the bitrate of lossless files because it's not something that gets set by the user. MPEG2 on the other hand, the bitrate is user settable can usually range from 2Mbit/s to 15Mbit/s, though most standalone devices won't go above 8-9Mbit/s on the highest setting since after figuring in the audio stream, that puts you around a DVD recording time of 1 hour per disc.
Could be that the unit you are using is being misrepresented here, a better way to probably convey how much space files are taking up is to post the number of GB (gigabytes, not gigabits) per hour of your captures.
As far as differences per capture in a variable bitrate format, it could be that one source was less noisy. Recording just a blue screen, for example, should have a much lower final file size compared to actual video with rapidly changing scenes. For fixed bitrate formats like DV, a blue screen recording would still take the same 25Mbit/s no matter what.
