Yeah, it's really close though. I feel Holtz will score more goals while being a very good all-around player. But I think Mercer has the possibility of being a Mark Stone-like player who impacts every aspect of the game. Everyone talks about Mercer's compete level and all-around play and sky-high hockey IQ -- with good reason -- but all this talk really seems to obscure the fact that Mercer is actually incredibly skilled. He's got an insanely good set of hands and he's an all-purpose offensive threat, with impressive ability in the passing and shooting departments.
I would not argue too hard with someone who ranked Holtz as the Devils #1 prospect, if only because he has 40+ goal ability, and this is certainly a rare and valuable commodity. But my personal opinion is that Mercer is at the very least a can't-miss, two-way, all-situations second-line stud; and he possesses an underrated upside which, to me, is in the Mark Stone stratosphere.
If I had to rank the Devils top 5 prospects right now (graduating all current Devils regulars like Smith etc), it would be:
1 Mercer
2 Holtz
3 Foote
4 Bahl
5 Mukhamadullin