Once both are set for mostly accurate colors, the 8350/8345 will have a brighter and more accurate picture, but it's hard to say whether or not it'll be a noticeable enough difference. The full-color brightness difference should be noticeable (advantage for the 8345/8350), but a good room and the available gamma control on the Optoma can make a dimmer picture not a big issue.
The Optoma will have advantages for fast-motion, gaming, perfect convergence, 3D, and lamp-life as well as price I believe.
If you are okay giving up the analog inputs, the newer Optoma hd141/hd26 finally added multiple user saveable settings so you can set up one for accuracy and one for watching sports with some lights on.
The upcoming brighter and more accurate hd151/hd36 might also be a possible choice if you can stretch your budget slightly over $1000.
Personally, I can't stand the screendoor pixel look of Epson LCD and would have to go with the DLP, but many don't mind the pixel-gaps as much and are more outspoken of brightness differences.
Actually if you're asking individual opinions, I'd move the mount forward 3ft and keep the w1070, but I'm guessing that isn't an option.
Benq really needs a wider release of the longer-throw w1070 (w1400)..and DLPs in general should start putting feet on both the bottom and tops of projectors for rear-shelf mounters.