If the price were equal, I'd for sure choose the HS20. I believe the contrast has been measured a little higher on the HS20. Certainly, the brightness can be significantly higher (996 vs. 615). Also, the HS20 doesn't wash out in bright mode -- so that brightness is definitely usable brightness. This means is will produce a punchier picture. The extra brightness will help the Sony hold up better on a grey screen -- improving it's (apparent) contrast even more -- while enabling deeper blacks and depth.
The power zoom and power focus are also nice features to have. With the 1.3 power zoom, a constant height screen is a possibility. Though many will prefer the installation ease of the lens-shift Sanyo has to offer.
Dust blobs and VB have been the negatives on the Z2 so far. (And, there's no apparent resolution to these issues).
Panel misalignment and start-up problems are the negatives of the HS20. It sounds like these issues are being addresses through repair/replacement. (Minor misalignments are not affecting viewing enjoyment).
After adding these issues up, I decided to pay the extra for the Sony.
gp