At those kinds of power levels it is not surprising, you would be on the trailing end of the curve and lumens should actually be dropping as you add more power at that point according to this: https://farm8.staticflickr.com/7567/16071892179_7d89411e10_o.jpg
Using them side by side, both in the 55-60 watt range the S70 does take noticeably longer to heat up. Makes sense as the head weighs 25% more. To the naked eye the tint plays a larger role then lumens.
I just ran a test on them actually to see what the difference is. At basically the same power level, on the same keeppower 4200mah batteries fully charged to 4.20v. I turned them both on turbo (and kept resetting the S70) and let them run for a bit over 7 minutes. They started out within ~150 lumens of each other and dropped about 100-150 in the first minute or so.
I checked the temp with an IR gun and they both rose at about the same rate except the L6 was always about 5-10f hotter then the S70.
After about 5 minutes the L6 was around 115f and the S70 was around 105f and the temps had pretty much leveled out. by 7 min and change the L6 was at 120f and the S70 112f.
I then retested light outout and they were basically the same again, interestingly they were closer after the test, about 100 lumens difference. Total lumen loss was around 300-350.
When I pulled the batteries both sets were at 4.01-4.03V, so the lights really did use almost the exact same amount of power, so the test is about as fair as it can get.
One thing I did notice is that to my hand the S70 “felt hotter” in some ways because of the smooth ano finish. I guess it transfers heat better or something. The Ir gun tells the real story.
They are both great lights, honestly they are quite hard to compare because they are so dang close.
I did run a little experiment the other day after modding them and showed them to some people to see what they thought based on looks alone.
It was 100% unanimous, The L6 won the looks contest hands down. They all said the S70 looked cheaper and felt “low end” due to the slick ano.
For a performance aspect they all preferred the L6 beam as well, they all pointed out the donut hole in the S70 as odd. Most of them also preferred the L6 3a tint as well when compared side by side.
To the layman the only feature that the S70 had over the L6 was the lighted switch, although once I explained that the L6 blinks when it’s battery is low they said that was ok as well.