One player vs three players at a table

I've been playing at Casino On Net, 4-deck game. It seems to have good rules for an online casino. I'm not a mathematician but it seems that I win more games playing three players at a table vs just myself (one player). I was wondering why?

Does this make sense? Playing with three people in a 4-deck game is the same as playing one person with a 1.3 deck game (4decks divided by 3 people = 1.3 decks). So playing with three people with a 4-deck game is the same as a 1.3 deck game for each player. However, if I play alone, I'm playing with against 4 decks.

Is my reasoning good, or off?