You're still talking hypothetical, wouldn't it be like this if it were, and so on. I look at what they can do and the basic luffy is clearly superior. There is nothing more normal than comparing the endurance of the Seraphim to the kaido. Seraphim have the greatest stamina in the OP universe, they can't take damage unless they put out the Moon Flames and no one can hurt them, you forget that the author of this series is Oda Oda decided that Luffy should use Gear 5 there and drew it that way because they needed to see him in that scene. Actually, there is no need to mention all this, luccinin didn't stand a chance against Gear 5, he didn't even manage to resist, this difference normally shows that lucci can't fight g5, luffy's comfort in fighting Saturn in the last episode is very revealing achievements, but if it needs to be clearer, I don't understand how strong you think lucci is, even luffy's g4 form before onigashima is at yc1 level,
So how can you think that luffy needs G5 over lucci?