I saw the 100 at Cedia and the only difference I saw between it and my 900 was the brightness. If you have a good room, I say get the 900. Also, you can get the 900 from Costco which is a huge advantage with there service policy.
As far as the Pearl, it is clearly in a different league from what I have seen of it compared to the Panny's. Like I said, I own the 900 and I saw the Pearl at Cedia on a verry similar size/type screen to the one I have my 900 on at home. There is simply no comparison. For one, no VB on the Pearl which is huge in my mind. Both my 900 and the 100 I saw had the same VB, and it is distracting to me. 1080p vs 720p was a noticable improvement as well. I dont know if it was the resolution exactly or the higher fill factor of SXRD, but the picture was much cleaner and fuller without having to use smoothscreen. The Pearl should be better though as it is in a different price cat. One advantage to the 100 though over the Pearl is brightness. It is a much brighter projector if you have a large screen, non dedicated room, or simply want more brightness. However I did notice that this additional brightness made the VB stand out a bit more to my eyes which some may notice, some may not.
The 900 overall is a great bang for the buck projector and I am sure you will love it. Even with the issues I have had, it has provided lots of great moments over the past 6 months. If you need more brightness, go for the 100.