It depends on what source you believe.
If you go by the IIHF they're both 6'0 and Eiserman is 9 pounds heavier (194 vs 185).
If you go by their regular teams then Celebrini is nearly 6'0, Eiserman 5'11, and Eiserman 2 pounds heavier (191 vs 189).
And they were similarly sized to each other while at Shattuck together.
Neither is substantial enough to determine which is "certainly stronger, more physically developed" based on their measurables. Nor is it the point.
The point isn't that they'll forever be similarly sized, but that the early posts that "Yeah, he’s had a crazy size advantage for a couple years" were always framed in a way like he was this huge dude dominating his peers because of his size, and it'd catch up to him as he played bigger and older players. It hasn't (so far) and he wasn't demonstrably bigger than other top peers then or now.
I'm not bringing up Celebrini to argue who is better. Not relevant whatsoever. Just pointing out that this legacy physical maturity notion that gets brought up is selectively applied. They're both elite prospects and favorites to be in the running for #1 overall next year. I don't care about prognostication beyond that. I'm just excited that (at least for now) it looks like we have some more elite prospects to look forward to as fans and a potential battle for top draft position again, which is fun compared to drafts where the #1 is a foregone conclusion during the draft season (i.e., Bedard this year).
I will say though that you should watch Eiserman more though if you thinks he lacks dynamic ability.
Not really. While he could have maybe played at the WJC, USAH has never selected an U17 player for the WJC in my 20 years following the tournament. They don't even really consider them, regardless of their forward group options.