what would be higher quality, the tv boradcast if it was captured or Jap laserdisc?
The Jpn Laserdisc: provided that Laser Rot hasn’t ravaged the disc… It has Dolby Surround and even in NTSC, superior picture quality to a TV recording which would be in mono because the BBC didn’t begin unofficial, limited NICAM broadcasts till the following year and made on a VHS/BETA tape that might be worn out.
Are you sure the UK broadcast & Japanese LD has extra footage? IMDB doesn’t mention any alternate versions.
It’s possible - because extra footage does exist…
There are seven minutes of deleted scenes on the Blu-ray and the Jpn LD reportedly has a running time of 108 minutes:
https://www.lddb.com/laserdisc/24025/SF088-5099/Santa-Claus:-The-Movie
The US LD is listed as 104 minutes:
https://www.lddb.com/laserdisc/09571/I5054/Santa-Claus:-The-Movie