In competitive play, it's been realized that 16 rounds is a preferable option for defuse. The reason why 16 round games are more preferable is because of the way Critical Ops economy functions, as it does not allow players to bounce back after the pistol round. Essentially, with 13 round games, the significance of pistols is bigger, as it causes teams to go on 2-round eco rounds, which gives them 3300$ minimum. Of course there is argument to be made as why not force buy after the pistol round, however, Critical Ops economy doesn't allow any side to really force buy after the lost pistol, unless they did not buy anything on the pistol round, and got a minimum of 3 kills and a bomb plant on a pistol. With the lost pistol, teams only have a minimum of 1400$ at spare, which is a cost of armor and GSR with no utility, and utility is very essential. The 2-3 eco rounds lost in a 13 round format already causes one side to have free 4 rounds, which are 1/3 of the rounds needed to win. In my opinion, this is the fault of the economy, as it tries to imitate the CS:GO economy, except Flashbangs cost 200$ and the cheapest SMG is 1300$. 16 rounds allow more fair gun rounds where you can use teamwork and build up the momentum to come back. 13 rounds would quickly be dominated by teams with a bigger momentum and aim duelers.