One thing that will often come up when discussing players from the early era of hockey is the concepts of amateurism and professionalism. Specifically, the idea that amateur hockey is somehow more pure or honourable than the professional game which began to emerge in the early 1900s. Pro players are sometimes portrayed as greedy, money-grubbing blackguards who care not one whit for the integrity of the very endeavor which fills their dirty little pockets! Phew, I think I had an attack of the vapours, there. I'll just go have a little lie down on the chaise longue.
That's better. Read biographies of certain early hockey players and you'll see references to them remaining "staunchly amateur" throughout their careers, possibly even turning down offers to turn professional at times. The implication is always that this is a noble character trait, that is says something about the player's makeup that he wasn't willing to sully the wholesome sport with filthy money and all it brings. This is ridiculous. Whether a player remained amateur throughout his career is a mark neither for nor against him. There is nothing inherently despicable about professional sports.
Arguments that amateur players played solely for the love of the game don't really hold water. Amateur hockey leagues were rife with arguments, petty squabbles and politics. Hardly a week would go by without some game or another being protested by the losing team on some (often frivolous) grounds or another. Nobility went out the window as teams and players traded barbs, each accusing the other of misdoings. Sometimes a team would refuse to play a game due to some unresolved issue. Sometimes a team or teams would quit the league entirely over some apparently minor thing. At least in the professional arena, teams had incentive to play every game they were supposed to, since there was money on the line.
Ultimately the distinction between amateur and professional sports comes down to class, a social concept given a great deal of import in the Victorian era when organized hockey was developing. Amateurism was considered to be the ideal, at least by those in the influential upper classes, because only those in the upper classes could devote a great deal of time to sport without expecting recompense for it. If you were in the working class, it was more difficult to take enough time away from work to become one of the very best in a particular sport, without being able to make money doing it. The origin of the special place amateurism is supposed to hold in the sporting realm is very much elitist in nature. It was intended to keep the riff-raff out.
I think (or hope) that we're beyond that now. You do need to consider a player's status when analyzing their careers, of course, in the sense that amateur players tended to have shorter careers, since they had less incentive to keep playing as they aged, and this shouldn't be held against them. But there's nothing inherently good about being an amateur, and nothing inherently bad about being a professional.