After reading the spec sheet I came up with two questions. Zombie, with your next level knowledge maybe you can answer these:
1. The spec says the LEDs arrangement is RGBB. Do I recall correctly that Blue is the weakest LED so they have to use two of them to make up the difference? Did the PF1500 have a second blue LED?
2. The contrast ratio is listed as 250,000:1. The 51A and other lamp based Optoma 4Ks are listed as 500,000:1. This info is on a list sheet of all there projectors that was handed out at the booth. The UHL55 features description lists "Dynamic Black Technology", "This feature gives more depth to your image by smoothly adjusting the lamp output to create a stunning high contrast ratio". I thought this function worked better on LED and laser projectors than on bulbs. The bulb projectors are listed at 2400 lumens while the UHL55 is 1400 lumens. So you have a faster dimming mechanism and lower light. Why wouldn't the contrast ratios be reversed? It doesn't make sense unless the bulb projectors have a mechanical iris. Unless Optoma wants to sell more bulbs. Seems like the 55 should have a contrast ratio approaching the UHZ65, which they list as 1,200,000:1.