I once owned an Arc 4+, bought an HDS and keep thinking about a Novatac just for more lumens (or modding my HDS). While the switch was problematic on the Arc 4+, the basic design elements of the light - the UI, clicky switch, options menu, etc... the legacy of which continues in the HDS and Novatac lights, remains remarkably well thought out and useful, and has spoiled me for a lot of other lights. When I got my HDS, and after testing it for a period of time to make sure it worked reliably (hey I was a bit gun shy after the Arc) I sold I think 4-5 other lights as those bases were covered with the HDS. No question if I could only have one light it would be an HDS/Novatac light. Well built and once programmed (or heck just used at factory default settings) it is pretty simple to use. I like to be able to toggle directly to most settings quickly, and I like the low low and the placement of really optional features (strobe, sos, etc...) where they should be, in an options menu. The build quality is excellent and I've never had a problem with any aspect of the light not being done very well.
But they are expensive lights relatively speaking, and not for everyone. I recently purchased a Liteflux LF5 and from what I've seen, the LF lights have the closest UI to an HDS/Novatac that isn't an HDS/Novatac. At around 1/3 to 1/2 the price, it is a good value and overall a pretty sweet little light. If it had a switch it would really be a stunner. Still, it is not at the same level in terms of build quality, etc... but for many it is certainly good enough, and the Fenix lights are much the same (although I don't like their interface as well, but the P2D and the two stage AA lights are the best of the bunch, relatively).
I don't know what the proper comparison is, because it is not just brand name, there is a distinct difference. Maybe the question is whether that difference matters enough to pay the additional money.