Scrapper Or Brute
Scrappers get more benefit from /Shield's damage buff aura, and do more damage with Lightning Rod and Shield Charge. So that particular combo is generally better on a scrapper.
In addition to what was said above, Shield comes with a very strong aggro aura, that's one of the advantages of going brute rather than scrapper out, and doesn't hit any resistance or HP cap, that's another possible brute boon gone.
So, scrapper. Definitely.
Wanting to make a Elec/SD toon and originally was going to make a Brute, however I was curious on if a Scrapper would play out better instead.