I'm trying to decide between these two (not for home theatre, but for classroom presentation) Epson projectors. The EX70 is 1600X1000 with 2000 lumens, and the EX71 is 1024X800 with 2200 lumens. There are minor differences in the lamp life, similar feaures, but is the difference in resolution significant? The lumen count? The 71 seems to be a replacement for the 70 which is discontinued. Any advice would be appreciated.