I prefer Angela because yes, she does hit like a truck, but her signature ability is pretty useless... i haven't played much with hela, so i prefer Angela
Angela and hela are both amazing damage dealers. I'd go with angela first, as she can do good damage fairly quickly. If you're skilled at charging heavies with hela, she can be one of the best options for LoL. I saw a video of a solo of LoL SL, she was doing 50k crits with basic attacks.
EDIT: here's a link to a reddit post with the solo: https://www.reddit.com/r/ContestOfChampions/comments/8eti6k/r5_hela_w_cosmic_supremacy_synergies_vs_lol_sl/
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Angela also has healing and she can be used in almost every part of the game.
does she have to be duped
Nope.
EDIT: here's a link to a reddit post with the solo: https://www.reddit.com/r/ContestOfChampions/comments/8eti6k/r5_hela_w_cosmic_supremacy_synergies_vs_lol_sl/