It all comes down to aesthetic preference. Do you want CG screen-accuracy or do you want a modern redesign?
Perfect Effect’s take is a bit more proportional and heroic in appearance but is a bit harder to find now. Transart’s own is an accurate replica of the show. It’s up to you on this one. I prefer the Perfect Effect’s take though I might get Transarts as well
Transart would be your best bet then. You’re in luck since it’s new so it’s easy to find. I think it’s in stock on ShowZ right now.
For me the character comes through more in the perfect effect version. The transart just looks more like a toy to me. I would love to see a chrome/vacmetal version of the PE one. If your interested in more transmetal figures your definitely best going with transart. They keep pumping out new figures and I am sure we will see their TM2 Megatron at some point (probably sooner than later).
I think the Nemesis Gorira variant is available on TF Robots NL’s website. 2 in stock. Edit: they have regular Beast Gorira as well.