The titan had a very visible texture that produced a shimmering that VERY noticeable on bright solid scenes, think light blue skies in movies or most solid textures in video games. This drove me crazy. From what I've seen, this is a symptom of cheaper screens and you're going to see it to some degree in most entry-level screens. The Reference 4k on the other hand is absolutely invisible. There is zero texture, everything is sharper and clearer due to this. Also, my Titan developed some slight waviness but where I moved to a fixed frame on the Reference, I'm not going to call that a "Win" as the Retractable reference could be just as likely to exhibit that.
All and all, when I first got my projector I was wowed by the size and the film like quality but quickly started to pick up on the negatives like the texturing and the sharpness. I still loved it but could see the flaws and felt while it was huge, my plasma delivered a much better overall picture. Once I switched the screens out my opinion changed immensely, my proj was now delivering a picture that I was 100% satisfied with. That was a year ago and I'm still very pleased.
Both screens were the Matte White standard gain option (1.2 for the Titan, 1.0 for the Reference). I also owned the Matte Grey manual pull down for about a week and that was plain bad. The mechanism broke very quickly and tore the screen, it had the same texturing as the titan, and my projector was nowhere near bright enough to overcome the grey.