Keeping this in consideration, should I learn e4 or d4?
When it comes to controlling the center, moving to 1. d4 would clearly be the best option. The reason is quite simple: d4 can control two central squares when e4 can only control one.
Secondly, does Carlsen prefer e4 or d4? Sicilian Defense
Sicilian Defense is the most popular, highest scoring response to 1. e4. d4 is statistically better for white is because there is no Sicilian Defense against it. It is no surprise Carlsen has to face the Sicilian on daily basis in many his games.
In respect to this, why is e4 more popular than d4?
e4 opens diagonals for two pieces while 2. d4 opens only a diagonal for the bishop. For this reason, 1. e4 is often recommended as a better opening if you're trying to learn chess.
Is d4 a good move?
d4 was considered a perfectly fine first move in the 19th century. However the other moves that are considered top tier nowadays (1. c4, and 1. Nf3) were considered bad at the time, as they didn't provide enough center control.