The I-W supressors are just the same as the suppressors on all the other guns.
Now, this is where it gets confusing: Look at the descriptions of the suppressors, which ever desription seems better to you, use the other suppressor.
Basically, if you like the way Suppressor 1 is described, use Suppressor 2. its a flaw made by Zipper which i think they admitted to but havent fixed. basically the descriptions are opposite. I always use Suppressor 1 because it looks cooler but thats the only reason over using the other one.