I'm quite surprised people are considering Mules to be dark sounding - I think they're classic PAF and thus quite a bright pickup. I don't have any problems with them in my Les Paul.
I've seen the Mules described as both bright and dark, same with several other BKP models. I found the Crawlers quite dark but I remember Blue saying he found his "incredibly bright"!
I guess it's all down to differing guitars, amps and individual perceptions.
That seems to fit my Mule experience. I originally put them in an Epi LP that, I believe, is basswood with a maple cap. In hindsight they were overly bright for me there - I wasn't getting a "plummy" warmth I was kind of expecting to go with the "bite".
Now that they're in my Love Rock, and I'm used to them, I am getting exactly what I was hoping for. I'd say I find the bridge bright, with body, but the neck dark (still with enough clarity on top, though). Out of all of my guitars, this is the one that needs the most careful tweaking of amp patches so that both positions perform for me - trying to tame the top end of the bridge can muddy the neck if I'm not careful. But when I do get it right... woooo!! :D
I'm still leaning towards Riff Raff (out of the pups I've tried) as my recommendation for Bamboofrog though.
