With the room you describe the JVC is by far your best option. JVC's are built like tanks compared to the Epson's. The sole reason I would swing toward the Epson is if your usage is high as the cost of replacement lamps on the JVC's is excessive and I still read people replacing them after 1000 hrs or so because they dim rather quickly. As far as ambient light as long as you have directional spots in the viewing area without any white surfaces you should be OK.
"Smart enough to know better, to old to care" ------ Dedicated Bat Cave Home Theater, JVC RS49U/Mitsubishi HC7900DW Projector, 110" 16:9 Jamestown screen with variable power masking for CIW 2.50:1 to 16:9, Marantz 7009 with 7.1.4 Atmos with Ohm mains,3 DIY Subs (2 15" (1 ported, 1 sealed and a 12" 4th order bandpass), 1 DIY butt kicker, Custom Built HTPC, 18TB DroboFS NAS