It's personal preference tbh. The best version of Dragon Ball Z currently available (to me) is the Dragon Ball Z dragon boxes. The new Blu-rays are cropped pieces of shit, that have over-saturated colours and are DNR'ed like a mofo, but are better than the "Re-master" Dragon ball z sets that are cropped too (The blu-rays aren't fully released). The Dragon boxes are frame by frame restored with the original aspect ratio and nothing touched besides the footage cleaned up. Dragon ball Kai or "Z Kai" is a refreshed Dragon Ball Z that cuts out all filler materiel and is much closer to the manga. The grain is removed and the home video release of this are completely uncensored like any home video release. It's been DNR'ed to give it a more modern look (But still looks much better than the DBZ blu-rays imo), but kept it's original aspect ratio. Kai is only just now airing the Majin Buu saga, so it's incomplete.
For fun, watch Dragon Ball Z abridged by Teamfourstar, or if you want you can finish up to the entire Frieze/Namek Saga in about 10mins with their Dragon Ball Z Kai Abridged.