Except you don't know what composition snake mesh socks are. nor do you know the weight of them. Though we do know the length of them. And the approx size of a helmet. The Helm covers approx 1/2 of your skull or .5 head lengths. The human body is generally somewhere between 6-7 head lengths, with the lower legs being 1.5 head lengths.
So comparing the helmet to the socks, its 1.5 head lengths vs approx .5 head lengths. In terms of "no downside" There is quite a heavy down side to the socks, and that is capacity. Even if the socks are not super obvious or anything like that, you're spending 2 of your additional armor value for /just/ additional armor value. Now to you and all your players and such, they might not care at all about anything more than just having the highest armor value there is, and to them, they won't see a down side to spending their points on just increasing armor value.
Second skin provides Ruthenium Polymer Coating, and Two capacity in addition to adding the two points of armor
Forearm guards provide 1 armor and 3 more capacity.
Secure Tech PPP provide 1 armor, 1 capacity and are quickly interchangeable, even if they do provide a 1 point penalty to social limit. And there isn't anything there that says they loose the capacity to go under pants.
Helmet provides 2 armor and 6 capacity.
Mask provides 2 armor and 8 capacity and +1(2) increase to social limit for intimidation tests.
Socks provide 2 armor, and +2 armor on specific called shots to the legs.