Anime shows are a team effort. There are many people involved in the making of your favourite show, each with their own style and take on your favourite character. Dragon Ball Z is no exception.
MisterSatanZ recently made a great video that takes a look at how Dragon Ball Z changes from episode to episode, depending on what animator drew it, and it's fascinating to see the comparison images side to side. Let's take a look:
You can watch the video here if you'd like, though do note that it's in Spanish:
While I knew that Dragon Ball characters have changed looks over time, it's fascinating to note changes in a smaller scale, too. Undoubtedly, you will have preferences for a certain take on a character -- I for example really love the hair on the Katsumi Aoshima take on Vegeta, which tilts his hair off to the right side a little bit. Other artists, meanwhile, don't seem to match the level of detail and quality that fans want out of an iconic anime like Dragon Ball Z. That's come up a whole lot in the wake of episode 5 of Dragon Ball Super, which features some pretty rough fighting scenes. The reasons for this are varied, as we note in that post. There is style to consider, then there are time constraints, and there are money considerations too, nevermind the dire working conditions for animators in Japan. But, it's also worth noting that even the original Dragon Ball Z had ugly visuals from time to time:
MisterSatanZ notes that this lack of detail in the show isn't always a problem, though -- it all depends on what the scene calls for. Here, for example, we're looking at a quick background shot. It's not the prime focus of the scene, so it's not as necessary for the visuals to pop -- even if they do look a bit silly out-of-context.