i think Farrell more likely to bust also (if a very late 4th can bust). In fact, since they're both competing for Top 9, feels illogical to say Roy has higher upside but bigger chance of bust. If he has higher upside, presumably also greater chance of being an NHLer to begin with. I'd think it more likely if competing for different roles but they're not really. Curious why you think that?
Higher ceiling, lower floor.
Farrell could settle as a defensive forward, I don't think Roy could.