When using sgRNA, there is no need for annealing crRNA and tracrRNA duplex prior to use. More importantly, several studies have showed that sgRNA has better stability than crRNA:tracrRNA when duplexed with Cas9, thus leading to higher editing efficiency1,2.
1. Hendel, et al., Chemically modified guide RNAs enhance CRISPR-Cas genome editing in human primary cells. Nat. Biotechnol., 33 (2015) 985-989.
2. Ryan et al., Improving CRISPR–Cas specificity with chemical modifications in single-guide RNAs. Nucleic Acids Research, 46 (2018) 2: 792–803.