Same director, same no-budget MMD animation. Plenty of ad-lib, seiyuus telling bad jokes and going out of character. "I think this is a pretty weird thing to be recording at ten in the morning."
Tesagure Bukatsumono will probably come out as the stronger of the two, but Gdgd Fairies is likely the easier one to get in to as it has less metahumor, banter and bullying but more slapstick instead. The cruder visual style of Gdgd Fairies is also likely to be easier for a newcomer to accept.
Both shows focus on cute girls talking about random subjects humorously.
Both shows are not very mainstream outside of Japan.
Overall, if you enjoyed laughing with one, you'll likely enjoy laughing with the other.
Plot? What's that? Story structure? Never heard of it. Fourth wall? Who needs it? Behind each show's art styles and settings, these are stories about a group of young women who pass the time playing silly games and talking about the weirdest things. Both shows also have very interesting (and in my opinion entertaining) approaches to absurd visual comedy.
gdgd Fairies really is a one of a kind anime and so finding a similar show is difficult. I'd say the main appeal of gdgd though is the conversations between the three primary girls that take place. Based on this I'd say K-ON! could be a good alternative as this is also primarily driven by the conversations made by the female cast, although with K-ON! it is 4 girls which later grows to 5. The humour differs a fair bit but the overall tone in both is light-hearted and fun.
Both series are 3D animated children's shows with an off kilter style of humor; Kemono Friends is more of a road trip show with an ominous backstory, whereas, Gdgd Fairies is an episodic slice of life series where its comedy is oddly dark for the intended demographic. However both series are rather thematically similar. Gdgd Fairies is more of a dark slice of life version of Kemono Friends.
Both are CGI series with short episodes. Both feature bizarre CGI and surreal humor, but while gdgd Fairies is more relaxing, Popee the Performer is more brutal. Both are underviewed because most people don´t pick it up because of the animation, but if you won´t get sidetracked by such a thing, you should try these two.
Both series are about 3 female characters talking about random stuff, animated using low quality 3D CG. The type of skits used in each show also have very similar traits. IE, both shows have a location where the characters can create anything they want in a giant open area.
Koutarou Ishidate's ad-libbed nonsense comedies are decidedly not for everyone, but if you find yourself laughing out loud at the absurd conversations, meta jokes on top of meta jokes and deliberately terrible animation of Naria Girls, I cannot recommend gdgd Fairies enough. The grandmother of it's own genre, gdgd Fairies is the first of Ishidate's improv shows and in many ways still the best, with a variety-like setup that makes the adsurd segments come naturally, a set of great VAs playing off of each other and an abundance of spectacularly horrible CG segments utilized to great effect.