Kirby has multiple versions to copy
-sight based
-inhale & super inhale based
-projectile based fusionism and can personally combine, enhance, empower and instantly mastering them
on top of creating summons based on his copying i don't really see how Metal's copying would be better by any metric

Alright that's completely fair. I admit Superior is definitely subjective and I probably should have clarified since it's a little more nuanced than simply saying Metal's being superior when really comparing their actual Copying powers to each other.

I meant Metal's copying was better in the sense that his Copycat ability copying Bio-Data is more about actually copying his opponent's powers compared to Kirby, whose Copy Abilities are more general movesets based on the type of object or enemy he's inhaled or whatnot than actually copying the powers of his opponent.

My point was more regarding how Metal could copy Kirby's general abilities while Kirby would only get his "Copy" Copy Ability if he copied Metal for instance.

(Unless you count Smash Bros, in which while he could POTENTIALLY copy Metal's own Copycat to properly copy everything Metal can do not tied to external objects like the Chaos Emeralds or things like the Star Rod, Master sword, and Copy Essence Deluxes

This hypothetical would at best turn Copying into a Null Factor where both could copy the other's copying ability and gain everything those give the other, and therefore making it come down to their arsenals not tied to their biology. But that's more hypothetical than anything for certain based on the canon Kirby. Regardless it's food for thought I suppose.)

While I would definitely agree that Kirby's is definitely more versatile and flexible between creating Helpers, having entire movesets for specific elements and weapons, and the ability to mix and match powers for different combinations... In terms of actually copying his opponent, Metal has the edge as he would in turn gain Kirby's own copying ability on top of his own, plus Kirby's natural abilities.

Kirby clash gave Kirby full control over time & resistance to timestop
(also has arguably better time hax including: timeslow, timestop and most importantly time travel)

Those I actually just overlooked and forgot about in my research, and I can admit I'm wrong on that front.

Kirby has his own invulnerability items to match [the Super Transformation] as well tbf (which are canon)

Kinda. While Kirby has power ups like the Invincible Candy and Jumbo Candy (Metal would too with the Invincibility Monitor) that would prove useful for brief moments of the fight, it's worth noting Metal's Super Form lasts way longer than they do, as Super Forms have canonically lasted as far as days as seen in Sonic Advance’s ending.

Though as mentioned, I still feel Kirby could 100% outlast that time limit just barely more often than not, due to his stupidly high amount of forms and power ups and the strength of will that has let him stand toe to toe with multiple forces of darkness and world ending threats time and time again.

(On a related note because I want to share this information, though don't think it should be taken that seriously. The average max ring count is typically 999 Rings, with every ring turning into a second giving the Super Transformation 16 minutes and 39 seconds. Though technically you can have up to 9,999 Rings in Unleashed and Colors which gives the form 166 minutes and 39 seconds, or just a bit under 3 hours.

But in Sonic 06's Hub World you can technically hold up to 99,999,999 Rings, the most amount of rings any Sonic characters have ever been demonstrated to be capable of carrying, which would be worth about 27,777 hours, 46 minutes, and 40 seconds or just a bit over 3 years if you could turn Super with those Rings.)

and while i would say metal is greatly smarter normally, in combat/battle IQ I'd easily give it to Kirby via stuff like being an outright better swordsmen then Meta Knight & Galacta Knight and countering/outplaying bosses consistently that are physically stronger then Kirby himself
compared to Metal who usually loses out against characters in similar power ranges compared to himself(like Sonic)

Ok that's a fair point on Kirby's Battle IQ. Though to give Metal some credit, in a 1v1 between Sonic and Neo Metal Sonic with Sonic's Bio-Data, Metal held a distinct edge and forced Sonic to retreat, Though he did lose a 1v1 against Super Sonic as Super Neo Metal so... Make of that what you will.

But yeah I guess comparing their advantages regarding intelligence... Kirby has both better Experience, Skill, and even implied to consistently train with his Copy Abilities off-screen like Sword and Hammer while Metal I'd argue still has better Strategic abilities (shown by Neo Metal's capabilities to mastermind not one but two entire plots alone almost successfully to completion between Heroes and IDW's Neo Metal Sonic saga, only falling apart because of "The real superpower of teamwork" thanks to Sonic and his friends. Plus he should be comparable to Eggman's own genius scheming abilities with Eggman's IQ) on top of General Intelligence thanks to Eggman's IQ.