2910 has - better build quality, DVI & HDMI outputs, 216 MHz 4:4:4 12 bit Video DAC's, Adjustable Chroma Delay and Level, 8MB drive buffer (layer change), DVD-Audio and SACD, Full Digital Bass Management for DVD-Audio & SACD, Pure Direct Modes, and last but not least did I mention Better Build Quality.
I tried both, the 1910 is half the size of the 2910 and at least 1/3 the weight. The 2910 is just an overall better unit.