Isn't that the same judgment that determined Shotaro wasn't physically strong enough to be Philip's partner?

Nobody's perfect. But Shroud is allowed that miscalculation, as she created the tech. It does nothing (major) to my opinion and faith in Shroud's judgement. Besides, it's probably only maternal reflex.

I understand your nitpicking KRX, but Shoutaro exceeded their expectations to begin with and proved to be the most ideal partner for Phillip. If Terui was that candidate, they certainly would have shown it by now. It's almost like saying that the maker is 100% right and that their creations are not capable of doing things beyond their comprehension. There are plenty of fictional and non-fictional cases of this happening... it's a story trope that happens all the time. So unless proven otherwise, it really isn't anything significant other than a good "what-if" situation.

We have established that Ryu is as capable as Shotarou. Shotarou may have exceeded expectations, but CAX would still be slightly more functional. I realize I may sound like the creator is 100% right, and I know it's not always true. But let's face it; Shroud had every right to underestimate Shotarou after working with Narumi Soukichi for years. Shotarou's good, but he has a long way to go before he's Soukichi good.

I fail to see how any of this is Decades fault.

Decade's lack of a FINAL KAMEN RIDE: D-D-D-DOUBLE card has left us debating on whether CycloneJokerGoldXtreme or CycloneAccelXtreme is Double's final form.

There is nothing saying that. You're placing CAX on a slightly higher pedestal based on one (And only one) line. Shroud considered CAX to be the better form. Until we see CAX in action, there's nothing to support her word on whether she's right or wrong.

Shroud said, and Philip and Ryu proved, that CAX would be more functional because they would be immune to attacks like those of the Terror Dopant's.

Again, to repeat what Matrixbeast said...there is NOTHING to prove that Shroud's word was the correct one...and in the end, it does not matter cause CAX never made it to the screen. And again, i'ts impossible to measure how strong a form actually is based on words alone.

You walk up to a person, claim you're the strongest person in the universe. But for all we know, you're actually weak as hell. You can't claim that something is so powerful without evidence that it is.

I think I can see where KRX is on this one. According to Shroud CAX would be the strongest form. That statement carries ALOT of weight due to her involvement in developing Skull, W, and Accel. Better than anyone she should know W's true potential. Just because it never happened in show and Shoutaro was able to stay Phillips' partner, it doesn't mean that CAX would be weaker than normal Extreme.

And I know that game appearances don't count really but CAX did appear in at least 2 games if I recall because it's weapons are the Prism Bicker and Engine Blade that it uses simultaneously. Based on actual appearances by normal Extreme, and the lack of one by CAX, we can never really know but I think for now it's safe to say we should stick with normal CJX or Gold for W's final and most powerful form.