Half and half. I like alts because you're looking at the product of a a theoretical scenario. However in practice, I'm not a fan purely because I can't use the alt and their original in the same squad. For instance, I like Skadi's S2 for both versions but with OG Skadi, I tend to use her with Utage S2. For Skalter S2, I like using her as passive healing and buffs (and her summon) for the cases that medics might not exactly cover.