It is fun reading this for sure.
One note on Caps Ridge. Sure it is a high start and sure the numbers also say 2700 ft gain in 2.4 miles but that really isn't telling the tail of the trail is it? The true trail or the real work starts soon after the Kettled Rock overlook. The last 1.4 miles is where the gain is on the trail.
Anyway it is fun to talk of the trails. Another factor is also age and weather conditions that the hikes were made in can make them seem easier or tougher on any given day.
I am happy to live fairly close to the playground.
I agree that climbing over the Caps is tough, but from the first Cap to the summit is 1300' over a mile, an average of 130' per 10th of a mile. Weather and age and physical shape of the climber are definitely factors on any hike.
I mentioned the North Slide on North Tripyramid earlier. The actual climb is 1200' over 1/2 mile. That's an average of 240' elevation gain per 10th of a mile. This pretty much beats everything including the Headwalls, although it is much shorter.
Someone else mentioned the Flume Slide Trail. From the foot of the slide to the Franconia Ridge Trail it rises 1400' over 7/10ths of a mile, which would rival the steepness of Huntington Ravine.
We've only been talking steepness here, not difficulty. This is what the first paragraph of the AMC White Mountain Guide has to say about Huntington Ravine Trail:
"Caution:This is the most difficult regular hiking trail in the White Mountains. Many of the ledges require the proper use of handholds for safe passage, and extreme caution must be excercised at all times. Although experienced hikers who are reasonably comfortable on steep rock will probably encounter little difficulty when conditions are good, the exposure on several of the steepest ledges is likely to prove extremely unnerving to novices and to those who are uncomfortable in steep places. Do not attempt this trail if you tend to feel queasy or have difficulty on ledges on ordinary trails. Hikers encumbered with large or heavy packs may experience great difficulty in some places. This trail is very dangerous when wet or icy, and its use for descent at any time is strongly discouraged. Since retreat under unfavorable conditions can be extremely difficult and hazardous, one should never venture beyond the Fan in deteriorating conditions or when weather on the Alpine Garden is likely to be severe. During late fall, winter, and early spring, this trail (and any part of the ravine headwall) should be attempted only by those with full technical ice-climbing training and equipment. In particular, the ravine must not be regarded as a feasible escape route from the Alpine Garden in severe winter conditions".