The 5050UB is a fair bit brighter and can handle larger screen sizes. It has a much better lens overall. This lens allows for much greater zoom range as well as a great deal of lens shift which can help with placement flexibility.

The big thing the 5050UB offers is better contrast with significantly better black levels. This has long been known to be a big factor with the 5050UB. It simply performs very well when it comes to delivering a better black floor and contrast with good shadow details. In a good theater space, with movies, the 5050 just does a better job than almost all of the DLP competition.

The 3550/3560 models are a good deal less money overall. They have a sharper image and handle gaming better than the LCD projectors really can do. Their motion tends to be a bit more detailed as well. Colors tend to be similar, but these models are not terribly bright and are best suited to about a maximum of a 120" screen diagonal before you start wanting more brightness. The black floor, as discussed, isn't as good as the 5050UB delivers. Due to the speed of DLP, this projector tends to be really solid with video games if you are into them.

Colors will be similar on both models, though the BenQ can sometimes appear a bit more accurate out of the box.

I struggle with the HT3550/60 models as I think I would go up to the X3000i or X3100i models instead, or maybe the X500i if it fits into your space. The inclusion of a solid state light engine (LED) makes a lot of sense for the long term and if you like gaming, these models do an exceptional job with that as well.