Both have examples of success in recent years.
Tampa Bay built a decade long contender and back to back Stanley Cup winner through great drafting.
Vasilevskiy was 19th overall pick.
Point, Kucherov, Palat, Gourde, Cirelli, Killorn, Cernak and Colton were all taken outside of the 1st round of the draft.
Carolina has been a consistent contender getting their two most important players in Aho and Slavin after the 1st round. Plus other important pieces outside of the top 10 in Pesce, Necas and Jarvis.
Dallas has been able to do a quick re-tool with their aging core by drafting Hintz, Robertson, Stankoven, Johnston, Oettinger and Harley all outside of the top 15 picks.
Bruins drafted Bergeron, Marchand, Krejci and Lucic all outside of the 1st round. They were also able to lengthen their contender window when they drafted McAvoy, Pasta and Carlo in a 3 year span, all outside of the top 10.
As for Pro scouting.
Florida is the best example. Adding Verhaeghe, Bennett, Forsling, Rodrigues, Marchment, Montour and OEL for cheap.
Vegas became an instant contender though the expansion draft.
Avalanche were able to add Toews, Burakovsky, Lehkonen and Nichushkin to help win the cup.
They're both viable methods but I'd give the edge to amateur scouting since it's a lot easier to find a star player outside the top 10 of a draft than being able to find a cheap star player though great pro scouting.
Even in the examples in favor of pro scouting, they all acquired their best players either though the draft or through a big trade/signing for an established star (Avs with Makar, Mackinnon and Rantanen), (Vegas with Eichel, Stone, Pietrangelo), (Florida with Tkachuk, Barkov, Reinhart).