Unless you are living under a rock , you may know the switchblade getting buffs back to back and now has risen in popularity a lot among the playerbase (mainly due to all the youtubers glazing it). But now the newly buffed iso is functionally speaking, a better switchblade (kinda).
Iso has better 4tap range compared to the switchblade while being more consistent in the second range. It has the same good feeling that you get with a switchblade with low recoil and the clarity of a red dot. It also has a bigger magazine at 50 rounds.
The areas in which the switchblade succeeds is in sprint speed, strafe speed and flinch resistance
For a cqc smg, flinch isnt a stat that you should prioritize, so the flinch difference isn't that noticeable. The sprint speed is just slightly faster, but you realistically won't even notice it. Leaving the only advantage the sx9 has being a faster strafe speed. Other than that, in every other field the iso is better
Forgot to mention, but if you have a good blueprint for the iso then you can use the long shot perk (yes the iso for some reason has the long shot perk) which will give it even more range