You dropping Ares is the easiest option. Mars-Amaterasu is the easiest way to hit Def debuff cap with either Ambush or Hercules, whileas Svarog-Uriel are some of the strongest Hime in the game once Awakened. Note that you can drop Mars and/or Amaterasu depending on content, since Ares obviously does more damage than either of those. But how well you can survive or deal damage (debuffs until Herc burst) without them is another matter, thus again, depends on content.
Svarog is absolutely insane. Not only does she give your entire team a 100% uptime 40% Assault buff, but her damage cap is literally broken. Let's have a look at some Hime:
Awakened Brahma: 720k cap, 6t CD (120k/t) (Awakening gives fuck-all to Brahma's nuke, her benefits are elsewhere)
Awakened Acala: 900k, 7t (128k/t) (only against Raging, massive 8.5 modifier)
Azazel: 650k, 5t (130k/t)
SSR Artemis: 520k + 300k, 6t (136k/t)
Awakened Susanoo: 704k, 5t (140k/t)
Awakened Ares: 875k, 6t (145k/t)
Svarog: 600k, 3t (200k/t)
Awakened Thor: 450k + 750k, 6t (200k/t) (note: extremely hard to hit cap due to non-multihit, second ability easy to cap at low HP)
Mammon: 190k + 190k + 700k, 3+7+6t (207k/t) (third ability supposedly easy to cap with Dartagnan's help)
Shiva: 600k + 600k, 5+6t (220k/t) (note: extremely hard to hit cap due to non-multihits, probably just doesn't happen particularly for the second ability)
Awakened Svarog: 900k, 3t (300k/t)
...
I mean, let's face it. It's obvious that they typoed Svarog's damage cap, and then they just rolled with it. Awakened Svarog's third ability is even more hilarious since it gives you 3x attacks every 3 turns, so... assuming you're not hitting that damage cap, Svarog is literally punching twice every turn. Plus the baseline 3*1 of course, so three times every turn on average. It's pretty difficult to find any Hime who can deal more than her, except maybe from the self-murdering Hime DMM has been releasing lately. But those will either kill themselves or require a fuck-ton of healing.
But again. Go with whatever you find the most fun to play. That's what games are for, right? Having fun will help your motivation, and Kamihime is a marathon.