Quality differences with 'best' and 'bestvideo' at 720p

[gitscrub]

Using 'best' downloads a higher quality variable bit rate file that can be up to 50% larger than the constant rate 'bestvideo' file. Is there a way to show the size of muxed files with '-F', or prefer 'best' if 'bestvideo' is used and its resolution is equal to 'best'?

Here is a random, less drastic example.

variable, 2344k - 3954k, average 2539k, muxed size 29.3MB

youtube-dl "https://www.youtube.com/watch?v=1Ffak4dYum0" -v
[debug] System config: []
[debug] User config: []
[debug] Command-line args: ['https://www.youtube.com/watch?v=1Ffak4dYum0', '-v']
[debug] Encodings: locale cp932, fs mbcs, out cp932, pref cp932
[debug] youtube-dl version 2014.12.17.2
[debug] Python version 2.7.8 - Windows-XP-5.1.2600-SP3
[debug] exe versions: ffprobe N-68289-g208c03a
[debug] Proxy map: {}
[youtube] 1Ffak4dYum0: Downloading webpage
[youtube] 1Ffak4dYum0: Extracting video information
[youtube] 1Ffak4dYum0: Downloading DASH manifest
[debug] Invoking downloader on u'https://r6---sn-8xgp1vo-2ia6.googlevideo.com/videoplayback?requires
sl=yes&dur=97.105&id=o-AOs4OKhad36Zd73ki_5lZvdRkhHyCYLVoXNd4vmJceyX&source=youtube&mm=31&itag=22&key
=yt5&ip=**.__..*&mime=video%2Fmp4&fexp=900064%2C900718%2C927622%2C932404%2C933226%2C9405434%2C
9406135%2C941004%2C943917%2C947209%2C947218%2C948124%2C952302%2C952605%2C952901%2C955301%2C957103%2C
957105%2C957201&ms=au&mv=m&mt=1419708506&sver=3&initcwndbps=1637500&sparams=dur%2Cid%2Cinitcwndbps%2
Cip%2Cipbits%2Citag%2Cmime%2Cmm%2Cms%2Cmv%2Cratebypass%2Crequiressl%2Csource%2Cupn%2Cexpire&signatur
e=FA0E18DA900E2D6ACA5D82F89F1F93B1FBCBB5A4.2CA8EEDAAA9060F9DBBF9EBAE10959DD08378F10&upn=Lbnzy71hCiw&
expire=1419730153&ipbits=0&ratebypass=yes'
[download] Destination: Chelsea vs West Ham 2-0 ALL GOALS AND HIGHLGHTS HD 720p (26.12.2014)-1Ffak4d
Yum0.mp4
[download] 100% of 29.38MiB in 00:03

constant, 2044k ('-F' incorrectly reports 2225k), muxed size 26.6MB

youtube-dl "https://www.youtube.com/watch?v=1Ffak4dYum0" -f bestvideo+bestaudio
-v
[debug] System config: []
[debug] User config: []
[debug] Command-line args: ['https://www.youtube.com/watch?v=1Ffak4dYum0', '-f', 'bestvideo+bestaudi
o', '-v']
[debug] Encodings: locale cp932, fs mbcs, out cp932, pref cp932
[debug] youtube-dl version 2014.12.17.2
[debug] Python version 2.7.8 - Windows-XP-5.1.2600-SP3
[debug] exe versions: ffmpeg N-68289-g208c03a, ffprobe N-68289-g208c03a
[debug] Proxy map: {}
[youtube] 1Ffak4dYum0: Downloading webpage
[youtube] 1Ffak4dYum0: Extracting video information
[youtube] 1Ffak4dYum0: Downloading DASH manifest
[debug] Invoking downloader on 'https://r6---sn-8xgp1vo-2ia6.googlevideo.com/videoplayback?id=d457da
938758ba6d&itag=136&source=youtube&requiressl=yes&mm=31&ms=au&mv=m&ratebypass=yes&mime=video/mp4&gir
=yes&clen=24841591&lmt=1419604862771843&dur=97.055&sver=3&fexp=900718,912334,912820,927622,932404,93
6117,9405712,9405934,942807,943610,943917,947209,947218,948124,952302,952605,952901,955301,957103,95
7105,957201&upn=3J9QtpvElYY&mt=1419708834&key=dg_yt0&signature=36FE2D6420D169AA7AF5FEC28E2F4DB862270
011.39164E1A807ACE894FDFD5F21C6ADAB5B47AB64A&ip=**.__..&ipbits=0&expire=1419730447&sparams=ip
,ipbits,expire,id,itag,source,requiressl,mm,ms,mv,ratebypass,mime,gir,clen,lmt,dur'
[download] Destination: Chelsea vs West Ham 2-0 ALL GOALS AND HIGHLGHTS HD 720p (26.12.2014)-1Ffak4d
Yum0.f136.mp4
[download] 100% of 23.69MiB in 00:03
[debug] Invoking downloader on 'https://r6---sn-8xgp1vo-2ia6.googlevideo.com/videoplayback?id=d457da
938758ba6d&itag=141&source=youtube&requiressl=yes&mm=31&ms=au&mv=m&ratebypass=yes&mime=audio/mp4&gir
=yes&clen=3096995&lmt=1419604825643156&dur=97.105&sver=3&fexp=900718,912334,912820,927622,932404,936
117,9405712,9405934,942807,943610,943917,947209,947218,948124,952302,952605,952901,955301,957103,957
105,957201&upn=3J9QtpvElYY&mt=1419708834&key=dg_yt0&signature=69E14CA8463159A8CEC817AF6051E82EF36313
E1.98A69DDA2831DB119A2340827A6CCCF583E20649&ip=.._._&ipbits=0&expire=1419730447&sparams=ip,
ipbits,expire,id,itag,source,requiressl,mm,ms,mv,ratebypass,mime,gir,clen,lmt,dur'
[download] Destination: Chelsea vs West Ham 2-0 ALL GOALS AND HIGHLGHTS HD 720p (26.12.2014)-1Ffak4d
Yum0.f141.m4a
[download] 100% of 2.95MiB in 00:00
[ffmpeg] Merging formats into "Chelsea vs West Ham 2-0 ALL GOALS AND HIGHLGHTS HD 720p (26.12.2014)-
1Ffak4dYum0.mp4"
[debug] ffmpeg command line: ffmpeg -y -i 'Chelsea vs West Ham 2-0 ALL GOALS AND HIGHLGHTS HD 720p (
26.12.2014)-1Ffak4dYum0.f136.mp4' -i 'Chelsea vs West Ham 2-0 ALL GOALS AND HIGHLGHTS HD 720p (26.12
.2014)-1Ffak4dYum0.f141.m4a' -c copy -map 0✌️0 -map 1🅰️0 -shortest 'Chelsea vs West Ham 2-0 ALL GO
ALS AND HIGHLGHTS HD 720p (26.12.2014)-1Ffak4dYum0.mp4'