Congrats! I see in your thread that the problem involved you not noticing an extra note in the base riff. I figured there must have been something else to the difficulty you were having in mastering it besides your actual skill level (compared to your previously mastered songs.)I got it!! See new thread on the main page.
I think it also supports my theory that variation in a songs note chart vs non-variation / more or less transitions / speed / etc, are more closely related to difficulty than the perfection required in mastering a song. Sometimes the two will go hand in hand though (solos like in "sunshine of your love" are difficult, varied, filled with rapid transitions and difficult bends, along with a fast-paced speed accompanying them, AND require a high % of correct notes to level)
I had a lot of trouble mastering "well ok honey" and "pumped up kicks", despite them being simple songs. HOWEVER, i would NOT mark these as difficult because of that-- the main issue was the fact that I hadn't exactly mastered the chords in the "bridge" or "breakdown" kinds of parts in the songs. In other words, if I really sat there until I could hit those parts at least 3 times in a row, at 100% speed, I would've mastered them earlier, despite the incredibly high % required to get 100k (it took 98% of notes hit to get 100.5k on "pumped up kicks" combo 1...)
Pumped up kicks I think is kind of an exception to the rule, however, simply because palm mutes don't give any groove bonuses-- so there literally is a ton of less room for error, especially with the fast chords they throw at you after playing two thirds of the song. But again, if I had mastered them first (which I still have yet to hit 100% of them consistently), I can see it being much easier, despite the high % of accuracy demanded.
I know this is all subjective, but one last example I have behind my thinking is "This Love" by Maroon 5. It's another "easy song" that's somewhat difficult to master (or was), but when I forced myself to sit down and hit the chorus chord section at least 5 times in a row, at 100% speed, I mastered it the first time I played it. Also chords tend to have more leniency ability because they can register extremely late at times and also register when you blatantly hit the wrong chord (but are in a nearby area), while fast solo's often require more precise timing and note accuracy.
Thus I would rate songs mainly filled with difficult chords more easy than songs with rapid-fire varied solos (carol of the bells solo 2, painkiller-- a lot of the solos-- hangar 18 - lot of the solos) etc.
These are kind of extreme examples, but if you were to ask me to compare two songs in difficulty, I could probably explain it better why I would think one is more difficult than the other (though I'm not sure anyone would care ) Just my 2cents