I have the GH25, and use it with a D750 or D500 and 200-500mm lens. It works well. It does double duty as a multi-row panoramic head, although you have to add a double Arca clamp (which they should have included). It does have a few issues:

1. It uses the horrible black grease used in lots of cheap Chinese gear (although even some Manfrotto gear uses it as well). Very sticky, not viscous. I tore down the horizontal bearing and cleaned it out, replacing with a good silicone grease. I left it in the vertical bearing for damping, because the vertical bearing does not have a friction adjustment (it's indexed).

2. Speaking of the vertical bearing, it's indexed. Which means it will lock securely in fixed positions. The first one I bought, however, was misaligned so it wouldn't lock at 90 degrees. I got them to arrange a swap at my local camera store; the replacement is fine.

3. If you mount the head on the horizontal indexer, you need to use an Arca plate (they provide). This is a single point contact, and it has a tendency to work loose if you use it as a gimbal head while mounted on the indexer. I fixed that by drilling holes in the base and using the Arca security screws as a second/third point of contact. You can get by without doing that if you realize that the indexer should not be attached if you are using it as a gimbal. I like a robust solution, and am always willing to drill some holes in my gear to achieve that result.

So what do I like about it? It's light. It works with lighter lenses (the telephoto zooms are okay). You don't want to use it with a 500 or 600mm prime lens...too heavy. And it comes apart and packs up very compactly (it's like the RRS head, only not as robust). So it doesn't take up a lot of room in my back pack, and hauling it is not a strain. I've used it for shooting the Burton US Open Snowboard Championship...you have to hike up the hill to get there.

I do not recommend the cheaper ProMaster (Wimberly style) head. That one is a real POS.

My other recommendation would be to consider the GH-13 gimbal head made and sold by Rob Pleas. It's a smaller gimbal head as well, not suitable for the big primes but great for the telephoto zooms. I've worked with him on some design changes from his original version; I think it's pretty good now. All roller bearings. Good Arca mount. Not a Wimberly copy. But US made (which is nice, when available). And inexpensive, and very easy to tear down to clean and lubricate. He has a nice flash mount adapter as well, if you are into the "better beamer" approach. There are some British heads, but most are Chinese. Not saying that's bad, but it's nice to get some American gear every once in awhile.

Why you eat a hamburger, not the steak? At least I can say, I have beef for dinner.
You can spend as low as $50 and perhaps cannot tell the difference; but you can experience a 360 degree Panoramic Gimbal. Which you might use less than once a year.
https://www.amazon.com/SHOOT-Aluminum-Panoramic-Telephoto-Supports/dp/B00IGOSBOE/ref=sr_1_6_sspa?ie=UTF8&qid=1525982695&sr=8-6-spons&keywords=Promaster+GH25+Professional+Gimbal+Head&psc=1

We don't pay extra if we don't care about the difference.
Usually is the case, you spend a lot more for a little better.
Most of us don't sell our captures, but just to keep good decent memories or to satisfy our enthusiasm.
If money is no object, I would spend them somewhere else before buying the best gears for my hobby.