So even if you'd recorded it during first broadcast, the Blu-Ray versions would show more detail?
If it was broadcast at 720p (or 1080i?), then you'll get a resolution increase on Blu-ray. You'll also not have so much compression that broadcast video has to go through. So, yeah, it will look nicer. Maybe not loads nicer but, short of remastering, that's about as good as Enterprise will ever look.
They're on iTunes in HD as well, aren't they? That's probably a closer comparison.
Right, the Blu-ray discs technically have the most detail possible due to offering full 1080p resolution on the live-action footage, in addition to using lower compression than the streaming/downloadable versions available (where are also only available at 720p resolution).
Enterprise was filmed on 35mm film, then scanned into 1080p for the digital editing workflow or for Season 4 it was shot at 1080p/24 on professional Sony HD digital video cameras. VFX was typically rendered at 720p for Season 3/4, a mix of 720p/480p, whatever rendered quickly enough in the time/budget allotted in S2, and 480p in S1. The VFX was then upscaled, if needed, in their editing workflow.
It was then prepared for 720p broadcast according to various places online. That the Netflix/Amazon/iTunes versions (and when shown on HDnet) are all 720p, lends credence to the information that it was indeed prepared for 720p during the first run broadcast of the episodes.
I'm a big fan of the Blu-ray sets since it is technically the best presentation we'll likely ever get of
Enterprise but more-so because of the excellent bonus features.
The reality is that Enterprise was shot pretty flat and dull at times (especially S1 and S2), so the live action doesn't have any major extra pop at 1080p, and the VFX is only rendered at 720p, so I'd imagine a lot of people don't feel a huge reason to get the BD sets since the 720p versions on Netflix, etc. do an decent job already.