The MGM issues will look identical to the SE DVDs/1990's VHS and virtually everything else older. The 1989 discs were repackaged into two box sets but with pressing dates 2-3 later so there may be some slight-very very slight improvement in transfer. The Goldfinger and Thunderball CAV boxes use these transfers with full CAV but with some added edge enhancement at least on TB.

The Criterion DN/FRWL/GF use show prints and are at 1.75:1 instead of 1.66:1 original ratio. The MGMs are correct.

Buying both box Connery boxsets is the easiest route, and nowadays can be had pretty cheap. Sound is all great, fully accurate PCM mono save for the title song in Goldfinger which was inserted as stereo instead of mono on all 1989 and onward MGM discs. The most worn audio is FRWL (lots of hiss but never detracts from presentation) and the most worn print is surprisingly DAF.

NSNA is only on a Warner letterbox disc, but I don't have a copy. I don't imagine it should look much if any different from the initial MGM DVD. The lossless original sound would be the draw.

As for advantage over later issues, you get the films as originally presented, warts and all versus the SE DVDs with compression artifacts/cropping on the first three films/Edge Enhancement etc./lossy audio vs. the UE/BDs which lose grain structure, color timing, have no lossless mono.

I'm honestly of the opinion that LD is still king on these titles.