It makes sense comparing Optoma UHD51A vs Optoma UHL55 because they both are able to give some premium features. Based on our rating, UHD51A has a total rating of 9.6 out of 10 versus 9 for UHL55.
Advantages Optoma UHD51A over Optoma UHL55
Bigger projection screen size: 30-300 inch vs 30-200 inch
Better brightness: 2400 vs 1500 lumens
More USB ports: 3 vs 2
Advantages Optoma UHL55 over Optoma UHD51A
Lower power consumption, 170 W vs 317 W
Longer lamp life (normal mode): 20000 vs 4000 hours