Talk about horses of a different breed.
The Optoma is a 4:3 projector with a dongle needed for component connections while the Infocus is a 16:9 projector with the 1024x576 DLP chip.
In my opinion, I would never buy a new display to watch TV & (primarily) DVDs on that is not 16:9. Yes, you can get the Optoma and get a 4:3 screen, then set it to 16:9 mode... which ends up using 1024x576 pixels. But, you will have light overspray and less efficient use of the light engine. Or at least, I expect that you would as this is something that hasn't been overcome in $10,000 projectors yet.
The Screenplay has a pretty good reputation, so of the two I would definitely go that way.
But, I wouldn't be looking at either if it were my money. The new Sharp XV-Z2000 is in the same price range and gives you the HD2+ 1280x720 DLP chip for well under 4 grand. It is designed and built by a company that has been making good home theater projectors for many years now which I think is a big plus. Not perfect, but very good for the money.
If my budget was tight, I would then look at the Sony, Panasonic, or Sanyo DLP projectors that are new this year. The Panasonic in particular has been getting pretty good reviews and offers incredible setup flexibility. No color wheel with LCD means no rainbow. LCD means contrast isn't as high as DLP... but the new LCDs are smokin' with contrast compared to a few years ago. Keep in mind that contrast is all about black level in which a very small change in black level equals a huge drop in contrast ratio... but not very noticable most often.
I'm not sure of all your requirements for buying a new projector or if it is 100% dedicated & installed for home theater use, but I would say definitely go 16:9 if it is HT use, and if possible, consider all you options and do some more research and question asking.
Read every review if you can - especially at
www.projectorcentral.com as there is a bunch of reviews there, including a recent article on the Z2000. Unfortunately in the last year they seem to be pandering a little more to manufacturers instead of being 100% honest with their reviews and getting into real world details. Regardless, you can get some good info there.
Don't set your heart on anything though - except a projector. Go "I want the best projector for my cash and I don't care who makes it." - That way you won't be favoring anything going into the buying fun.
As I said - not sure what your specific expectations are though.