It stands to reason that the pre-THX widescreen discs would be noisier, as they didn't have noise reduction applied (at least not to the DefCol level). DavisDVD has this to say about the DefCol:

One drawback to this CAV set is that the first film suffers from too much noise reduction (for an example of this see Luke's lightsaber during his training with the remote onboard the Millennium Falcon).
and this about the "Faces" edition:

Uses the same letterbox transfer as the "Definitive Collection" CAV box set, only with the noise reduction greatly reduced.

This would suggest that the "Faces" set should be a better source than the DefCol. However, Grinder's report about the pre-THX set notices:
- the absence of motion smearing, this is very evident
- the presence of stars, especially those in the opening shot of SW

so isn't it possible that these could be made to look even better than "Faces"?