Which is better, Counter-Strike Global Offensive or Tom Clancy's Rainbow Six Siege?

 All of the other answers have already covered most of the important points, but I will add just one more.Whenever I play a new shooter, one thing I look at is the behavior of a reload with an automatic rifle. For example, a common video game gun is the AR-15 pattern rifle, which includes AR-15s, M16s, M4s, and more. These types of rifles usually use a 30 round detachable box magazine that feeds rounds into the rifle. Now, if you are familiar with the operating principles of guns, skip a paragraph. If not, just read on.If I pick up an empty AR-15, insert a 30 round magazine, and charge the rifle, one round will be inserted into the chamber, leaving 29 in the magazine. I could then remove the magazine, and the chambered round would stay in the weapon. If I then insert a fresh 30 round magazine, The gun will have 31 rounds in it, and I won’t have to pull the charging handle again, since there is already a round chambered. This is commonly referred to as a 30+1 capacity. Since an AR-15 automatically chambers a new round every time it is fired, there will always be a round in the chamber until the last round is fired. If I have a rifle with 30+1 rounds in it, and I fire 5 rounds, there should be one in the chamber and 25 in the magazine. If I then reload, all I have to do is change magazines, and I’ll be back up to 30+1. If I were to pull the charging handle again, a perfectly good round would be ejected and the gun would have 30+0 rounds in it.One of the first things that I noticed about Rainbow Six Siege was that it correctly modeled the reload of an AR-15 pattern rifle. If the player fires some rounds but does not empty the rifle, the reload animation just changes magazines, but does not needlessly cycle the weapon again. In contrast, when playing Counter Strike: Global Offensive, the player will cycle the weapon every time they draw it, even if it was already fully loaded. This makes the game horribly unrealistic, but realism is not the goal of CS:GO. CS:GO revolves around consistency and repeatability, seen in the time to reload weapons, the fact that each team starts in the exact same location on the map each time, and even the time of day while playing.This was the most prominent indicator for me that Rainbow Six Siege was going to be a really fun game. R6S is loaded with details that make the game much more nuanced than CS:GO: In Rainbow, each team has several different locations that they can spawn in, with each having different routes to the objective with different strategies required.Overall, both games can be fun to play, but I prefer Rainbow 6 Siege because it involves more strategy and planning than CS:GO. CS:GO is fun as well, but it sometimes feels too twitchy when you round a corner and instantly get jump-awped by someone 100 feet away.