Idealism is more Rational than Materialism

[Rational AKD]

We gain confidence in our perception when that perception is supported by evidence, by the result of trial and error, and by the concordance with others' interpretations.

you only gain the evidence by perceiving it. you are essentially saying your perception of reality is accurate because we perceive it...

The fact that we share a common understanding of reality supports the claim that there is one.

no, sharing common understanding of reality supports the claim we have a common perception of reality. we still don't get to statements about reality with common perceptions.

Maybe you can, but it would only exist in your mind.

not necessarily. my view on idealism is that there are distinct yet similar minds (which are what we are) and they are part of a greater consciousness (which is what God is). I explained all this in the OP, I suggest you read it.

Again, no. The evidence of shared experience says you are almost certainly wrong.

just because we all perceive the same thing doesn't make it any more true of reality. we know matter doesn't have color, it is merely a perception. it is a simplistic model to explain a more complex concept of wavelengths.