Improve the quality of webm video using ffmpeg

Question

I'm trying out two codecs and was wondering if I could improve the results of the webm output ...

ffmpeg -i test.ts -t 10 -f webm -vcodec libvpx output.webm

to match the quality of the mp4 output...

ffmpeg -i test.ts -t 10 -b 1500k -vcodec libx264 output.mp4

What settings would give me the best webm rip?

Thanks.

Edit: Here is an error output when trying some rip improvements...

ffmpeg -i test.ts -c:v libvpx -crf 4 -b:v 1M -c:a libvorbis output.webm

ffmpeg version 0.8.6-4:0.8.6-0ubuntu0.12.04.1, Copyright (c) 2000-2013 the Libav developers
  built on Apr  2 2013 17:00:59 with gcc 4.6.3
*** THIS PROGRAM IS DEPRECATED ***
This program is only provided for compatibility and will be removed in a future release. Please use avconv instead.
[mpeg2video @ 0x9cde5c0] mpeg_decode_postinit() failure
    Last message repeated 4 times
[mpegts @ 0x9cda240] max_analyze_duration reached
[mpegts @ 0x9cda240] PES packet size mismatch
Input #0, mpegts, from 'test.ts':
  Duration: 00:03:59.53, start: 4630.845422, bitrate: 1977 kb/s
    Stream #0.0[0x20b]: Video: mpeg2video (Main), yuv420p, 720x576 [PAR 64:45 DAR 16:9], 15000 kb/s, 25.60 fps, 25 tbr, 90k tbn, 50 tbc
    Stream #0.1[0x28f]: Audio: mp2, 48000 Hz, stereo, s16, 224 kb/s

Unrecognized option 'c:v'
Failed to set value 'libvpx' for option 'c:v'

Answer 1

Resolved :)

LordNeckbeard posted in the comments https://stackoverflow.com/a/9477756/1109017 which clarified the confusing situation between ffmpeg and avconv.

Edited: based on comment.