Has anyone compared these two guns to see which one of them was the most accurate? Thank you.

You mean put them both in a ransom rest side by side to get a representative sample of one of each? And the point would be.........

sorry if its a dumb question.

I have fired both, but not side-by-side or in a direct comparison. Overall same lockup, same twist rate, same accuracy. The P229 is something like 5 oz. heavier and more controllable.

Not a dumb question at all Sir, if possible go to a shooting range and rent both, see which model YOU shoot the best, that could/would overcome any difference in accuracy between the individual models themselves.

I have to wonder of you're thinking about a church congregation.

I have shot my 229 at 300 yds at B26 silhouette targets and was able to hit it 6 to 8 times from 15 round prone supported. Ammo was 147JHP
Most handgun are accurate errors come from conditions and shooter

No comparison-
P229 Classic w/ 22LR,9x19,357Sig,40S&W top end options.
(I've packed one for 30yrs)

320-striker fired...Tupperware!

is the 229 a tighter fitting pistol because it is milled using a cnc machine where the 320 is molded plastic?

The 229 is heavier and has a better trigger both of which make it easier to shoot well.

No.

It's almost amazing that some guys still buy into the "tupperware" mantra. That was a valid question in the 80's and 90's, but polymer framed guns are well past proven at this point in 2020.

Also, the plastic part of a 320 is the grip module, which is just a polymer shell that fits over the functional parts. The slide is steel and it rides on steel rails, same as any other good polymer frame pistol.