Minami-ke Okaeri is much better than Minami-ke Okawari.
Rather than my usual template (characters, story, art, sound, enjoyment), since this is a sequel, I'll keep it very brief.
Minami-ke Okaeri is a much fresher version of the story of the Minami sisters. The art style has reverted back to the more bright and colorful atmosphere we grew to love in the first season, while the character designs seem similar to the second season. There is also a little less fanservice. The stories are as varied as ever, with much greater involvement of other characters. This season is also funnier than the second season.
Basically if you are a Minami-ke fan, you will enjoy this season, and will be happy to have gotten through the second season in order to get here.