A comparative test between various video compressors actually used.

An AVCHD (.m2ts) clip has been used as source about 1:47 duration and 119Mb size (screenshot).

The clip has been converted within Xilisoft Video Converter Ultimate software using an HP DV5-1030EL notebook with Windows 7 Ultimate 64 bit operating system using various profiles.

AVI format: codec H.264/MPEG-4AVC Bitrate 1200K VBR encoding, output: 119Mb (screenshoot)

AVI format: codec H.264/MPEG-4AVC Bitrate 3500K VBR encoding, output: 119Mb (screenshot)

AVI format: codec H.264/MPEG-4AVC Bitrate 128K VBR encoding, output: 85.3Mb (screenshot)

AVI format: codec MPEG-4 Bitrate 1200K VBR encoding, output: 113Mb (screenshot)

MP4 format: codec MPEG-4 Bitrate 768K VBR encoding, output: 119Mb (screenshot)

MPEG format: codec MPEG-2 Bitrate 2000K VBR encoding, output: 118Mb (screenshot)

WMV format: codec wmv3x Bitrate 1200K VBR encoding, output: 117Mb (screenshot)

AVI format: codec xvid Bitrate 1200K VBR encoding, output: 114Mb (screenshot)

Playing the clips once converted i didn’t noticed big differences except when the bitrate is enough low, it’s interesting to note that between a medium and an high bitrate there aren’t so much differences, the same thing between different codecs with the same bitrate.
Note: the clips have been played in the same notebook using VLC software and it’s not exactly the same of playing in a full HD tv.

A final note about encoding times: the compression with MPEG-4 and MPEG2 codecs has been very fast (some minutes), the compression with H.264/MPEG-4AVC and XviD codecs taken about 10 mins, the compression with wmv3x codec has been slow, about 20 mins.