Hi! I know what this is. I'm not a huge DBZ fan but I've heard what all this is about.
1. You cannot prove it.
Gt is non cannon. The creator of the originals didn't make GT, so even if you had a quote from him saying he is stronger, Toriyama can't decide. It's like the creator of one superhero claiming his comic is stronger than another one without any real proof.
2. Why can't they be equal?
Continually throughout the series the good guy is weaker than the bad one. Then the good guy finds a new form, and beats the bad guy. This is what happens, except the SSJ4 Goku actually beats his foe. The God Goku loses after he transforms.
3. Is god the last form Goku can take in the real series? If he is, then maybe in the non cannon series SSJ 4 isn't the last form and he can transform into the next form.
I'll be honest I was just board when I started it and true I can't prove it its more hypothetical and I don't think there will be a official SSJ 4 because of gt plus I was thinking that Omega could at the most destroy a few planets Bills could destroy the whole d@nm universe if wanted to on top of that SSJ God Goku was in space and SSJ 4 Goku never went into space.
Ok so space we don't know because Ssj4 Goku never went into space, but man think.
If Pikilo can destroy the moon when his power level is that low, (Like... 500-1000 maybe?) then don't you think they could destroy more than a few planets? Take Freeza for example. He destroys a planet and then starts laughing. It obviously doesn't take much energy.
He does this in his FIRST form.
Ok I almost decided to agree with you but the KEY difference between them is that Goku only held Super Sayan God up for a short amount of time. S S J 4 was on for a way longer time than Goku was as a God.
Also, he needed help to achieve this form.
If Goku as a ssj4 could just survive a couple minutes, he would beat SSJGod Goku.
The way this happened was the same reason Vegita got mad and beat up Bills: His loved ones were in danger. It shows a clip of his family in danger and fear of being killed. Gohan even does this when he beat up Freeza, attacked Nappa, beat up Raditz, killed Cell. This is nothing more than a trait the sayans have. When they get mad, and someone's in danger, they gain tremendous energy for a short time.
He would've been killed. Bills was using only 70%. Yet still: Vegita, is a SSJ2 and he beat up Bills with this Sayan power up. It doesn't necessarily mean that Goku still had God powers, only that he powered up from the family in peril thing.
Also he wasn't doing so well. He lost in almost the same amount of time at King Kai's planet, he only took more hits which couldv'e been from his when a Sayan gets beat up then healed they gain power thing. The only way he could keep up with Bill's speed was with instant transmission...