Your comment on deinterlacing is interesting, by film do you mean DVD ?
Deinterlacing is a big topic, and I'm deliberately trying to avoid getting into a detailed discussion of it.
But one important thing to grasp is that the approach used to deinterlace material depends on how it was captured in the first place.
Some sources were captured in a progressive format, for example by using a film camera. What this means is that the odd and even fields which make up each frame were both captured at the same moment in time: it started out as a single progressive frame which was then split into two fields. A cinema film works like this: the camera takes 24 progressive pictures per second, each of which is split to produce two fields. There was no time delay between the capture of the odd and even fields in the same frame, but there was a delay of 1/24th of a second between an even field and the odd field in the next frame.
But if you think about something like a live football match or news broadcast on British TV, the camera doesn't take 25 progressive-frame photographs per second: it takes 50 interlaced photographs per second. So there was a delay of 1/50th of a second between the odd and even fields, and then a delay of another 1/50th of a second between even and odd fields.
So, when deinterlacing you first have to decide if what you're looking at is "film" (i.e. captured progressively) or "video" (i.e. captured in an already-interlaced state), and the strategy you use depend on which it is. (I might add in passing that one thing which distinguishes deinterlacers is how good they are at telling the difference between film and video).
The Lumagen HDP is quite good telling the difference between film and video, but its ability to deinterlace video is less than top-notch compared to something like an Edge or a VP50. But both approaches will do an equally good job of deinterlacing film and of course the HDP's scaling is significantly better than the VP50's. So you'll find that the HDP will be more less unambiguously better for film, but for video it may be a more complex question. If what you watch is mostly material originally shot on film then the VP50 or Edge's superior video deinterlacing won't count for much; but if you watch a lot of football, then it might.
Obviously there are a lot of other factors to consider as well, like grey-scale correction, ability to get a good signal out of Sky HD, etc.