The Emerald is certainly more Rock than Blues, hence the Emerald neck is very much a modern interpretation of a more traditional PAF sound. The bridge Emerald is tight and bright whereas something like the Crawler is fat and smooth but with a real growl to the tone. They may be able to cover similar ground but they're very different beasts in my experience. One of the many things I love about the Crawler is its huge operating window. It splits really well, the cleans are fantastic and the distorted tones sublime. It will play Blues all day long and run all the way into Metal territory, covering everything inbetween. I never thought I would live to say this, but the Crawler has actually surpassed my beloved Holydiver and become my favourite Bare Knuckle pickup. In a dark Les Paul I agree, it has too much bottom end but if it's in any way similar to a PRS CU24 or Vintage V100, it will sound incredible. For neck pickups, I have no experience of the PG Blues but if Kiichi says it's good, I wouldn't argue. The Mule might also be a good one to consider as it's very similar to the Crawler and Abraxas neck pickups but a bit brighter. I used to run an Emerald neck with mine which worked really well as I like a slightly more modern cut to my pickups but I'm now running a Holydiver with the Crawler, which is a hell of a lot more vintage sounding than I expected and sits beautifully in that guitar.