Piracy: ꜱᴀɪʟ ᴛʜᴇ ʜɪɢʜ ꜱᴇᴀꜱ

Hello - I need some help understanding something. I'm looking at two WEB-DL files from reputable groups that are identical in nearly all ways (see details below), except one file is noticeably larger than the other (2.8GB vs 3.47GB, for example). I thought WEB-DL's should be the same size if they're from the same source (AMZN in this instance), so I'm a little confused as to why there's such a disparity in size when all else appears equal.

Any idea's what could explain the difference in file size here? I'm assuming the FLUX file is older based on when it was first uploaded vs the NTb one. Could this have something to do with it?

Bonus question: Which file would you choose in this situation?

(1) 1080p.AMZN.WEB-DL.DDP2.0.H.264-NTb

• FileSize......: 2.80 GiB
• Duration......: 42 min 35 s
• Video.........: High@L4 | 1920x1080 @ 9 197 kb/s
• Audio.........: English Dolby Digital Plus | 2 CH @ 224 kb/s
• Subtitle......: English / English.

(2) 1080p.AMZN.WEB-DL.DDP.2.0.H.264-FLUX

• FileSize......: 3.47 GiB
• Duration......: 42 min 12 s
• Video.........: High@L4 | 1920x1080 @ 11.3 Mb/s
• Audio.........: English Dolby Digital Plus | 2 CH @ 224 kb/s
• Subtitle......: English.

Edit: Thanks for all the replies! For anyone who stumbles upon this later on with a similar question, there's some really great replies in the comments below worth checking out. In my case, the file size difference was due to the difference in bitrate, where the bitrate differential is likely due to either (A) the region where the AMZN WEB-DL occurred (with different regions having different bitrates), or (B) the release group modifying the bitrate to fit a specific need (like limiting the file size). Knowing both release groups here tend to prioritize quality, I'm guessing the region is likely the main driver in the difference in bitrate size.