when I was shopping(around may) I brought a 1080p rip of MIB 3 with me to test out(it's got some half decent contrast/blacks, and the opening scene where it's moving quickly down the jail's hallways provides some content to assess motion handling on).
anyway, I couldn't really pick out anything from either set that was better or worse during playback. what I did notice was that the Samsung was a lot easier to get playing, haha. not a big deal though, it just took awhile to find the 'usb' button on the remote, that seemed to be the only way to access the video file. compared to the Samsung that basically popped right into the video folder when I inserted the usb.
I don't remember exactly, as I wasn't really interested in how either played video off USB, but there may have been some limitations on video settings while playing back usb content on one of them. the panny if I remember correctly. I could be totally wrong though, but it's something worth double checking if you intend to do that often. I just vaguely remember thinking I couldn't judge the usb content because one of the TV's didn't display it as well as a normal source through HDMI.
Displays: Samsung PN64F8500/JVC X35
AVR: Pioneer VSX-1018AH, 5.1 audio
Sources: HTPC(Mediabrowser), PS3, XBOX360, Wii, Sony DVP-CX995V
Control: Harmony One