9-18 Vs 10-22canon and 12-24 Nikon

Hi
Looking for any users that have owned any or all three of these lenses.

I have had the nikon 12-24 and really enjoyed it. Moved to Canon and currently have the 10-22 and find it good for my mix of pro and personal use.

Have stepped into the m4/3 camp with a couple of GX1 bodies and looking at getting the 9-18

Can anyone advise how it compares to the canon 10-22 in regards to sharpness, quality of build and ease of use...

It would be handy on the m4/3 but as I already have the 10-22 on a 600D is there any point in selling the canon gear to fund the purchase of the 9-18?

Thanks