Difference between rs505 and rs805 calipers?

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Is there, apart from the price, any difference between these two?
I was looking at buying the rs805 calipers, but they weigh the same, use the same hoses etc.

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I am now even looking at rs405 brakes, as apart from the color, I can't find any differences either... Though I probably won't risk it because according to Shimano they aren't compatible with r785 shifters. (while according to shops, they are)

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Pic links - BR-RS505 and BR-RS805 looks similar, I can't find differences. BR-RS405 looks similar, but it have different specs (non-ceramic piston)
Servo-wave levers ST-R785, ST-R685, ST-RS505 are compatible with BR-RS505, BR-RS805, BR-R785, BR-RS785, BR-R9170, BR-R8070
BR-RS405 officially compatible with non-servo-wave levers ST-RS405 - less strong caliper materials? (Servo output power - see last pic)
BR-RS405 uses same geometry as BR-RS505 (and BR-RS805), looks like the only difference is in body materials and pistons:
http://si.shimano.com/pdfs/ev/EV-BR-RS405-4020.pdf
http://si.shimano.com/pdfs/ev/EV-BR-RS805-3852A.pdf

[Ticlimax]

This exactly the information I needed, thanks!