PIU Difficulty scale vs. DDR/ITG Scale

Can anyone who's played both Pump It Up and DDR/ITG tell me how the PIU difficulty scale corresponds to either ITG ratings or DDR X ratings?

I've played songs rated 1-7 in PIU which seem similar to 1-7 in DDR.

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I'd say from my experience that 1-15 in PIU roughly corresponds to 1-15 on the DDR X scale. I can't pass above 16s in PIU so I don't know about above that. The highest rated song in PIU Fiesta EX is a 27, but I don't really think it looks like it would be a 27 on the DDR X scale.

In general, the scale used in Korean Pump mixes (Fiesta/Fiesta EX/Fiesta 2) and Infinity is a lot like DDR X's scale, but stays much more linear past 15. A KPIU 19 is still very passable, and of course there are charts up into the high 20's at this point. Pump Pro/Pro 2 brought the ITG scale over entirely.

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Based on my play experience, Korean PIU current stepchart rating = DDRX and above rating. I played 8 to 16-rated PIU stepcharts and they flow the same like DDR X charts.

I feel like I can compare the harder ITG charts to harder PIU charts SORT of. I feel like an S20 is either a hard 12 or an easy 13, 21 is a 13, 22 is 13/14, probably moreso 13, 23 is probably a 14, 24 is maybe a 15, 25 is maybe a 16? I'm totally guessing on this haha.

Edit: I'm speaking in regards to Fiesta EX 2011 ratings.