-Homing meganucleases are enormous and old-school
-ZFNs are compact (28:1 for input DNA:target) but obviously hard to target, so they may have specialized applications
-TALENs can be synthesized solid-phase, but they’re pretty huge (I think it was either 100 or 1k:1). The modularity is an improvement over ZFNs, which is why they were in fashion
-CRISPR are of course the best (1:1), although the extra machinery may be tough to deliver. Also, I’m curious as to the packing of the RNA–I feel like that might pose a problem for delivery?
In the end, an adenovirus can only carry about 4k, so CRISPRs are the most valuable.