system
Given the following post, respond as if you're commenting on Reddit:
human
What makes CRISPR better than other genome editing methods, and what makes it worse?
gpt
Most gene editing methods take advantage of local DNA repair mechanisms which are there to repair errors in DNA.  As you might expect, these mechanisms are more active when there is a problem with the DNA that prevents cells from reproducing, such as a break in a DNA strand.  CRISPR-Cas9 is useful because it allows people to create breaks in DNA strand that will cause DNA repair mechanisms to be upregulated.  To take advantage of natural DNA repair systems, we can insert a repair template that will get integrated in a targeted manner at the site of the break while it is being repaired.

Now of course, there were other ways to create targeted breaks in DNA before CRISPR was developed.  However, these methods were targeted by altering long proteins that binded to DNA in a sequence-specific manner.  The disadvantage of those methods was altering such long proteins was more laborious, so if you wanted to target a lot of different things it took much longer and was more expensive.  Also, those other methods tended to be less efficient at breaking DNA, so you have to screen sometimes thousands of cells before you would find one that got edited.  CRISPR is much more effective, and is easier to target due to only needing to change a few dozen bases in a targeting guide RNA sequence, which can be done quickly and cheaply.

One disadvantage of CRISPR-Cas9 is that while most of the DNA you want to target can be whatever sequence you want, the proteins have evolved to require a short sequence of DNA next to the target be a pre-determined sequence, such as NGG for the most common Cas9 protein.  This limits where you can target, and if there is no sequence nearby where you want to edit, then the efficiency will be much lower.

Another disadvantage is the sequences guide RNAs target are only around 20 bases long, which gives less specificity than other methods, which can target regions of around 40 bases and higher. This means you'll have more instances of cutting DNA that wasn't intended to be cut but looks kinda like the region you were interested in cutting.  However, there is a lot of research and engineering being done to reduce these off-target effects, so hopefully it won't be a real issue in the future.