if I may chime in here, although not currently being a Lumagen user:
My personal opinion matches Jim's (no surprise there). Basically I consider what the Arve custom curves do (and also the official JVC projector HDR implementation) really bad, from a color science point of view. I mean Arve did the best that was technically possible, but scientifically speaking, it's a bad solution. Here's a quick demonstration why:
These screenshots were made with a special test pattern I created which asks for colors which after YCbCr -> RGB conversion "overflow". Such colors should probably not be used in UHD Blu-Rays, but in reality they sometimes are. And what is worse: Tone mapping often turns perfectly valid colors into such "overflowing" colors. So although my test pattern is pretty mean, it's still valid to test for extreme situations.
What you can see in the test pattern above is how the test pattern should ideally be rendered (left side): All color bars should maintain their hue, just get brighter from left to right. On the right side you can see what the Arve type of color handling does to that test pattern: It totally destroys the hue! Basically red first turns into orange and then into yellow. Blue turns pink. And (you can't see that in this test pattern) green turns yellow, too.
Here's another image for you, this time real world material:
From left to right:
1) Arve/JVC color handling, tone mapped for a 4,000nits display.
2) Arve/JVC color handling, tone mapped for a 200nits display.
3) Proper color handling, tone mapped for a 4,000nits display.
4) Proper color handling, tone mapped for a 200nits display.
As you can see, Arve/JVC color handling renders a deep red for a 4,000nits display, but switches to bright yellow for a 200nits display. That obviously doesn't make any sense. Arve/JVC color handling isn't even consistent with itself. Depending on how bright your display is (LCD flat panel vs projector), it will either produce deep red or bright yellow. Proper color handling doesn't do that. Instead it renders the same hue, regardless of the display's peak luminance capabilities.
I have to admit, though, that the hue shifts produced by Arve/JVC color handling do make Mad Max explosions look more like what we're used to from other movies. But that is actually a lucky accident, nothing more! In this specific case the orange/yellow hue shift looks subjectively natural to our eyes. But in other cases such hue shifts can be very detrimental to image quality.
But instead of making Arve/JVC color handling look bad, we can also go the other way and showcase how much nicer proper tone mapping can look with real content.
was kind enough to make some nice comparison images here, using the The World in HDR
other AVSForum thread post with many comparison screenshots
The images titled "dynamic" were made with madVR's best quality tone mapping, which I expect should look similar to what the Lumagen does (?). The so-called "dumb" images are made with Arve/JVC type color handling. For comparison purposes I'd suggest that you copy the URLs of those images from the other thread and paste them into different browser tabs, to make quick back & forth switching possible, which will allow you to see the difference much better.
Contrast is a mostly separate issue to color handling, btw. Contrast will mostly depend on which tone mapping curve is used. Color handling instead decides whether there are any hue shifts, and how much bright + highly saturated colors are desaturated.