I have both. The LMG is a lot chunkier, which is both good and bad. You'll likely never wear it out, and I think all of the moving parts (recoil spring assembly, gas piston, gas regulator, bolt and carrier) being serial number matched is a nice touch. It feels extremely milspec. With the exception of not being full auto, it's exactly what the factory in China makes for export sales to actual armies.
Having been employed as a C9 and C6 gunner within sections in the past, though, I'm pretty much done with lugging LMG's through the bush unless I absolutely have to. For ease of carry and packing into your vehicle for a range trip, the folder is extremely handy. It's also built well: I have around 3000 rounds through mine and the only jam I had was magazine related. It seems to me that the folder is no less reliable, but it is perhaps, very subjectively, about 10-15% less "nicely built". It's far from unacceptable, and maybe mine is just loosening up from my round count, but the LMG has nicer finishing touches and just feels more solid. With this said, like I said, my folder has taken a beating over the three years that I've owned it and it's not failed me yet.
If you want a gun to shoot offhand and lug to your gravel pit, the folder will be a lot easier for that. If all you do is shoot off a bench at the range, the LMG is a good fit.
I'm very happy to have both.