Sorry TD for the long response, but I've put a lot of thought into your question.
The easy answer is that both of them want to play whatever position will allow them to play the highest grade (and the same could be said of most rugby players, truth be told) and that they'll play where they're needed in order to do so. I don't mean to be flippant with this statement.
The more honest answer is that for both of them it's too early to tell and where they eventually settle is probably dependent on a lot of factors, few of which have anything to do with their relative position-specific skill levels as very young (18 to 21 yo) front rowers. IMO the potential to go further and play higher (either within the club or professionally) is the greatest determinant of where they want to play, therefore the training they do, and therefore whether they're technically more suited to LHP or Hooker.
When we're talking LHP and hooker (not THP) as I'm sure you're more than aware, at club level (especially when young) there is a huge crossover and players can and will go back and forth between the two positions. Stephen Moore, Heath Tessmann, Lyall, Campbell, Paul Mousa (one for the purists), Palupe - all of these players have in the past, or are still playing both LHP and hooker at Premier grade/Premier colts level (or equivalent).
Players can have a preference for hooker and can tell you they're hookers, and they can do all of the training under the sun to be a hooker. But if an ARU scout says "hey we want to make you a prop - you have a better chance of being selected there in a Super Rugby or Australian side" 9/10 of them will say "ok - I'm a prop now".
(I think if you'd asked a 19yo Mitchell Wade what position he played he would've said "flanker" but the 22yo Mitch Wade after being approached by ARU coaches interested in making him a hooker now says "hooker" so now he's training his arse off, learning all the skills and techniques that will make him a top-flight hooker.)
My point is that we still don't know where Lyall & Campbell are more suited, because their skill is still being developed, any scrummaging or lineout technique they have is pretty basic, and their technique will largely be shaped by the training they are yet to do.
But as of right now both of them are saying they're hookers
