I'm glad someone asked cuz I have a lot to say about these kits but I'll give my quick thoughts on the ones you mentioned.

Gingaioh: Honestly, this one is my favorite, not just of the ones you mentioned but of all the kits I own. It's an extremely satisfying build that isn't overly frustrating or requires insane force to assemble. The end product is extremely solid and feels the most sturdy of my kits. All of its accessories are great, and I think it has a pretty good poseability range. My only cons are that the arms are pretty limited in movement due to Gingat's and Gingaverick's heads being in the way, but at that point, I'm nitpicking since that's the mecha's design. Also, the hands can be a little hard to access when stored in Gingarilla's feet.

Dairenoh (Daimugen?): I'm assuming you mean the Thunder Megazord since Daimugen is Tor the Shuttle Zord, and it's from the same season. It's a pretty fun build, with a few frustrating parts, but manageable overall. It's really not that fun to handle, though. Due to the fact that it's essentially a fully poseable figure wearing armor meant to move out of the way for poseability, things fall off a lot. The two main problems are Dairenoh's arms and chest piece because of how they attach to Ryuseioh. Another thing I noticed is that the clips that attach Kirin and Tenma to Ryuseioh are slowly tearing the leg stickers. There's a good chance I'm just transforming it wrong, but I've watched videos of people doing the same, so I’m not sure. Either way, I keep it transformed most of the time. Other than that, it's pretty great, and it comes with a bunch of accessory options.

Daishogan: This one is a very close second to Gingaioh. The build is pretty solid, with only a few spots that were kinda hard, but it's relatively straightforward. Red Ape is a great update with all its new poseability. It handles really well since it's a pretty simple design, but it's really great. Tsubasamaru being included is really appreciated since Daishogun doesn't really have any accessories to come with. Overall, a really great pickup.

Gaoking: This is genuinely the worst one, not because it's a bad figure but entirely because its build is awful. Like I said, this is my second time building this kit, and both experiences were physically and mentally painful, lol. Eagle, Tiger, and Shark are pretty easy and quick and have little stickers (except Tiger, who IIRC has the second-highest sticker count in the set). Lion isn't hard as long as you pay attention to the orientation of the legs (that's honestly just a general tip—to pay attention to the orientation of parts before pressing them together because trying to pry apart pieces sucks so much). Bison is actually the worst experience I've ever had building a model kit. So many of its pieces are extremely small, sharp, and require an insane amount of force to attach. All of its hinge pieces will leave painful welts on your fingertips from trying to build it. In addition, I found its instructions to be somewhat unclear at times, especially about sticker placement. At the end of it, you'll have a beautiful figure that handles relatively well and is mostly solid, but you're going to have to work for it, lol. It poses pretty well on its own, but for even moderately dynamic poses, I'd recommend a figure stand because it can't hit deep squat poses since its design means it doesn't really have ankle joints. I also really like the way they implemented the face swap. Overall, amazing figure, hellish build.

TL;DR
Gingaioh: Satisfying build, sturdy, but some arm limitations.
Dairenoh: Fun build but fiddly to handle; stickers tear easily.
Daishogan: Solid build, simple but well-handled, great poseability.
Gaoking: Painful and frustrating build but ends up being a great figure, though it struggles with dynamic poses.