Since the UT50 doesn't use an "Infinite Black" panel, I dont think it benefits from the improvements made to the 2012 ST/GT/VT models. I doubt it holds up to a VT30 since, to me, it doesn't look as good as even the ST30 did.
I really don't understand what you mean about the filter on the ST. It does tend to darken a bit off axis as it diffuses light but you make it sound as if the panel is matte.These are not LCDs we're talking about here... It's still a piece of glass and to me still seems pretty reflective. The louver filter is there to preserve black levels during daytime viewing and should not affect viewing in a dark room at all. The UT50 blacks tend towards gray under bright/direct lighting because there is no filter. At night it should also not look as good as the ST because it is a different panel.
ht Panasonic TC-P60ZT60, Monitor Audio: Silver RX6, RX Centre, Radius 90HD; Martinlogan Dynamo 700, Marantz SR5006, PS3, Oppo BDP-103D
2ch Marantz PM8004, Sony BDP-S1000ES, JVC T-X3 tuner, Monitor Audio Silver RX1, REL T3, Apple TV, Peachtree Audio DAC•iT
lr Panasonic 50ST60, Sony BDP-S5100