I run the same batches of the same strains through different Hoppers.
For two Hoppers (one Ti and one SS) I start at 2.5 and progress to 4.0. The SS Hopper will produce very dark brown and black ABV. The Ti will produce dark brown ABV.
For two other Hoppers (also one Ti and one SS) I start at 4.0 and progress to 5.0. The SS Hopper will produce dark brown ABV, the Ti Hopper will produce light brown ABV.
So with everything else being the same, some Hoppers produce darker ABV (and at lower temps) than other Hoppers. Range is from light brown to black.
Seems to be the nature of the beast...
Yes, I'd have liked to hear that the 'test' runs were all done using the same 'good' battery, at its' fullest state of charge. Sounds like a pain in the butt though.
Nonetheless, I like your comparisons and having experienced a lot of hoppers myself, I concur with your observations.
I don't take any issue with your 'Seems to be the nature of the beast' assessment! It's your post, in which you may subjectively muse all you care to.
You leave us all guessing as to effect. My guess is you're pretty equally ripped using any one of them...
I gravitate to the one that gives me the least draw restriction; this is one main factor that I've noticed going downhill over time no matter which hopper it is, and my unsubstantiated humble conclusion is that internal gunk-ing is one of the main hopper killers.
I have come to really dislike the uncomfortable amounts of heat these things throw off, both in vapor and 3 distinctly different ways from the body of the hopper; central body and mouthpiece build up heat simply from use, as-in more than one hit at a time; back-end 'short' that gives a hot shock to fingers, and; front end 'short' - when a finger touches body and front end simultaneously. Both shorting conditions are painful, period, like, ouch!
I currently have 3 short pieces of silicone tubing slid onto one of my hopper/pfe's and these are the main places I'll touch with fingers or lips. All this is on hopper with most draw restriction and I'm just waiting (and waiting, and waiting) for one or two to come back from warranty before sending this one back for re-grooving.