Just started watching. Gamera vs Gyaos is the headliner over Gamera vs Viras, don't you know. I've chosen "English Dub 1", which I think is the good dub. I'll know for sure shortly.
It's the good dub.

I'm going to write random comments as I watch and then post the whole lot in one post once finished.
"Is Gamera storing heat energy released by volcanic action, or is he already cremated?"
Gotta love the facial expressions on the two bumbling workers. Yes, definitely out of Hidden Fortress.
Ichy sounds like a girl! "You're a reporter, aren't you? I'd be disloyal to our villagers if I decided to help you out!" Hrmm, but if Gamera might be up there, Ichy will sell out his villagers in a heartbeat.
Ichy running in front of Gyaos's lair with Gyaos looking on, great and colorful perspective shot.
Round one! Fight! Gamera, do you want your arm cut off? Just hold your arm right there, don't move, and Gyaos will comply. Gyaos wins!
I promise I will not screencap Ichy riding on Gamera's back. "Gamera, this is fun!" Not seeing any embedded talismans on the shell.
"You refer to the new monster as Gyaos, did you not?"
"Mmm....I named it that cause....that's the type of noise it makes."
"Illogical." Did I hear that right? It must have been "logical", but I listened a few times and it certainly sounds like "illogical".
I like how they inform the viewer of the Gyaos rules. The tuning fork analogy and how he makes his beams, which the viewer then surmises is why his head is shaped like that. Between the zoologist stating how he has two spines and two throats, and the military guy responding that then Gyaos can't turn his head making his back a blind spot. As well as Ichy sharing his Gyaos log which shows that he only comes out at night, and therefore Gyaos hates light.
Round 2! Fight! Oh, no, poisonous yellow vapor! I thought I knew the Gyaos rules! Gamera: "Got your foot, Gyaos!" I like the vampire vibe here with the sun coming up, and Gyaos's ultraman signal on his head. Gamera wins!
I didn't want to do another screencap, but I really liked this perspective shot too with Gyaos eyeing his lunch.
Minor nitpick with the suits. I think they'd look a lot better if the teeth on both monsters weren't so pearly white. A little off-white would have done wonders, I think. Although Gamera was eating lava eariler, I think....
"No spins? That might just work! The way to immobilize Gyaos is to make him so dizzy that he can't move!"
And between the sketch on the wall making Gyaos look like a giant bat and the blood bird bath plan, they're going full vampire here. Gyaos is even sucking it up! Spin, spin, spin! But don't let go! "How long until sun rise?" "Three minutes."
I genuinely like all the human characters in this. Between the villagers trying to make big money on their land, the construction workers wanting to save their work site, and the scientists and the military personnel wanting to save the world, they're all acting believably making this a little more than a typical monster movie plot. Ichy is the link between all of them and the monsters, spurring ideas, and keeping the narrative moving along. The kid is a bit annoying, but he isn't front and center stage the entire time either.
Round three, fight! Now this is a fun monster fight! Green and purple blood! Tail trip! Gamera's on Gyaos's back! That's the weak spot to attack him from, just like the military guy theorized! "The end of the monster Gyaos." Gamera wins!
This is a good Gamera movie. Like Son of Godzilla last week, it finds a good blend of serious but not too serious. I think I appreciate the various subplots more each time I see this flick. This is probably the best bunch of actors they ever had in a Gamera movie. I still like Guiron more than this for sentimental reasons, but this is definitely the better kaiju movie.