Does viz bleach look better than viz naruto?
In my opinion, they're both very similar in terms of quality. The amount of upscaling they were able to do is limited by the source material being standard definition for both series. It's not going to look like a modern, native 1080p anime.
That being said, the improvements are there to see; the image is sharper and crisper compared to the DVDs, for both series. If I had to pick one over the other, I'd say the upscale is better on Bleach; in my viewing experience for Naruto I have noticed some artefacts, on a couple of occasions, running down the side of the image (against the black bars), which I'm guessing is a result of the upscaling process. It's not ideal, but doesn't detract too much as they're not present long and Naruto does still look good. The Naruto DVD masters were known to have a lot of funny business going on in them in terms of the image anyway; which the upscale does help to fix. I haven't noticed anything funky on the Bleach set yet.
Realistically, these are probably as good as it's going to get on home video for these series.
The biggest upgrade however, is actually in terms of the audio for both sets. Both sets have a DTS-HD Master Audio 2.0 track for both English and Japanese; meaning that the audio is lossless, resulting in a higher quality audio track. There's definitely more of a kick and greater clarity to the audio compared to the DVDs, which used compressed, lossy audio tracks.
I'd just be wary not to expect too much from these upscales. While they are on Blu-ray and upconverted to 1080i (Naruto) and 1080p (Bleach), it's clear to see that the material is from the early days of digital animation and originally created in standard definition. Despite that, the upscale is very much noticeable and looks good on both in my opinion.