Since the compression method sounds similar to ffv1, lets see how they compare.
My benchmarks on a random chapter of a random DVD I had on hand (Ghost in the Shell 2; mostly CG, cropped but not filtered)
YUY2 (because that's what all these codecs have in common), 704x384, 2000 frames
There were no duplicate frames in this clip, so that feature of lagarith wasn't tested. But note that MEncoder has a similar duplicate frame remover that can be applied to any codec, so ffv1, ffvhuff, and ljpeg would benefit the same amount.
This is just one source; YMMV.
Code:
Codec Bitrate Enc fps Dec fps
raw: 103705
huffyuv 2.1.1: 31524 93.41 71.61
ljpeg: 28965 44.85 45.63
huffyuv ccesp: 28170 96.48 72.54
ffvhuff: 24308 86.81 70.42
lagarith: 23242 41.08 29.88
ffv1(cavlc): 19756 27.99 26.31
msu: 17676 0.83 10.63
ffv1(range coder): 17221 23.23 25.77