You could say it's a completely different sport. It's hard to explain because at its core, it's still boxing. A ring, a ref, gloves, punching.

But what makes boxing boxing isn't punching each other in the face. The game is to win, and that game has rules which mean the world in terms of tactics and strategy.

For example, in Amateur boxing you virtually always wear headgear, in pro boxing virtually never.

In amateur boxing you don't get points for a knockdown, which can often be a dealbreaker in close pro fights.

In amateur boxing you can have a 3-round match, or a 4 round match. And a 4 round match will be two minutes. That's 8 minutes of fighting, versus Pro boxing where you can have 12 matches of 3 minutes for 36 minutes, that's a massive difference.

It's like comparing the sprint to a marathon, tactics and strategy aren't the same and while they're both running, they're a different sport. Amateur and Pro is a bit like that. On the other hand, it's not, because you can have multiple of such amateur fights in a single day, while the elite pro boxers fight once every 3 to 6 months. It's more like doing a marathon versus running multiple sprints.

Because of the headgear, the 30% shorter rounds, the much fewer rounds and the lack of points for knockdowns, amateur boxing is much more about scoring points very quickly, than doing damage and getting a knockout. It's really hard for two equally skilled fighters to get a knockout with headgear within just 3 rounds, especially at the young ages most amateur fighters fight at. Judges also focus everything on counting scoring blows. In pro fights, judges also take into account aggressiveness, ring dominance, initiative, punch volume etc, not necessarily on paper or officially, but it plays a bigger role in judging.

Lastly, the scoring is different. In pro boxing every round is its own battle, because you win or lose rounds, and those add up to your score that win or lose you the match. In amateur boxing, rounds are more arbitrary units, as you can't win or lose a round. The amount of legal blows you get on your opponent is added up for each round, and those get summed up. This difference opens up lots of different strategies.

Then there's tons of small differences. Things like glove weights and materials being different (pro is more spartan). Things like grease being allowed or not. A standing 8 count in amateur boxing (if you're in trouble, the ref gives you some time out, in pro you're fucked. You'll likely get a knock down and lose points, or a KO). In amateur fights can and often are stopped with bleeding and swelling, in pro it continues to a pretty extreme extent.

A really big part which is a bit ambiguous, are fouls. In pro boxing refs are very lenient about clinch tactics. Things like pushing with the shoulders, leaning on the head, stepping on the foot etc happen over and over again and only get warned late in the game usually when it's excessive. It depends on the fight and the ref. It sounds small, but they compleeeetely change the game.

Lastly, money. Pro's are of course, paid. And it's a career. That changes everything. It means that aggressiveness is part of your gameplan, not because it'll make you win, but because win or lose, you'll get paid more the next fight. Amateur boxing is a different world, more olympic, no money, a focus on the win above all.

Anyway any boxer will tell you they're completely different sports.