For me, coming from the JH13 pro, the merlin didn't impress me that much. Soundstage and bass would go to the Merlin, but they sounded a little veiled, recessed and dry on the whole. Can tell the merlins were aiming for a specific presentation but seemed to fall short in most aspects. With the Heir 8.A in the picture, lets just say, the gap is even wider. Soundstage is still comparable with 8.A, but bass not nearly as enjoyable. And if you find Merlin's bass too much, may need to consider elsewhere cos 8.A's bass is comparable if not more so, in quantity and quality. But given how precise the bass is delivered, you might actually like it more than Merlin's bass delivery.
The merlins did sound better, especially bass had better presentation and clarity, when coupled with twags. But the improvements are minimal.
Same can be said for Miracle, although the Miracle is better in its overall presentation. But to my ears, it still fell short of how music is delivered versus the JH13. It's a different piece, and probably better measured against JH13 pro instead of Heir 8.A.
This is the part you're probably asking about and i'll just sum it up in the following sentences,
The Heir 8.A is what Merlin was trying very hard to achieve.
The JH13pro is what Miracle was trying somewhat to achieve.
My preference would be (1. being most enjoyable to 4. least):
1. Heir 8.A
2. JH 13pro
3. Miracle
4. Merlin