That sanyo 4500 lumen LCD will be great if you perform with a lot of ambient light. If you anticipate performing in dark environments, a DLP like the optoma you chose will have deeper blacks. Also most DLP projectors have a sealed light engine, which means no dust can enter and dirty up the image. LCD systems are not sealed and seem to be a bit more fragile. You do get better brightness with LCD projectors in general, though.
Also make sure your computer can handle outputting the native resolution the projector requires. I sometimes have to dumb down my show to run on resolutions like 1280x800(WXGA) when I design for my projector at 1024x768. If you are running a lower resolution backbuffer to compensate, you might as well have gotten a lower cost/brighter/lower resolution proj.
That Sanyo looks nice though, although you might want to look at something with a zoom-able lens for more flexibility (if you care about resolution).
I’d look at 1024x768 projectors too, unless you absolutely need the high res.