I just recently got the 410HLF and have been very impressed with it. And I recently tested it with 4 different heads and found that it can definitely be much different sounding, depending on what you're putting through it.
- The Peavey MK VIII and Trace Elliot AH350 both sounded very clean and clear, plenty of low and highs and you can dial mids however you want.
- SWR SM-400S and Yamaha B100-III with their parametric EQs were a bit muddier and harder to dial in "my sound."
To me, though, that sounded like the nature of the beast with the amps, more so than the cab.
I did compare these to a GK 410BLX (sealed cab, no horn) and definitely found it was a different sound. The amps where I had trouble controlling the paramids seemed to be exacerbated without having the higher and lower frequencies afforded by the horn and porting.
One thing I will say about the 410HLF is, it's a bit of a niche market for these in some ways.
First off, it's a 4Ω cab, so most amps would only be able to use one of them. Granted, same thing with the 810, so I think they basically designed it like the "smaller" version of something like that. But it doesn't get the "modular" aspect you'd see with doing something like 2-4x10 cabs separately.
Speaking of size, too, it's quite a bit taller than "the average" 410:
(though unmarked and repainted, it's on the left)
If someone were considering doing a 2-4x10 setup for the ability to split in half for either portability or modular aspects, the 410HLF isn't gonna be part of that equation (unless they want 2 large 4x10s and have an amp that will run 2Ω easily).
I did have an 810 many years back and it sounded great, though a beast to move around. And I recently had the match to the GK here, running a 2-4x10 setup with that. There is definitely a difference in sound between those and this HLF. I'd almost equate it more to the HLF being voiced kinda "hi-fi" and the traditional 8x10 being "classic but still clean."