I have enough ascension materials to ascend one purple. I have both Victor, and Sartana. In your experience, which is the better hero in most situations? Why?
Sartana because she deals proper damage and has solid stats for both offense and defense. 
She’s a very good purple hero to ascend as your first 5*.
Victor for the speed and secondary special effect of +30 % team defence.
But you’re not going to go wrong either way. Sartana is quite good.
Mostly depends on team makeup and if you need a heavy duty sniper or if team defence and a finisher is required.
To me Victor is better as he improve your team’s survival, counter perfectly annoying heroes as Kunchen and hits faster than Sartana, other than having better tile damage.
Going for an all attack route would also greatly improve his DoT and he also is a nasty last man standing for wars.
I chose Sartana. She’s good. She can hit hard.
With Victor, you need to stack 2-3 hits on the enemy to kill them. And even then it takes a few turns for the damage to reach killing levels.
Sartana won’t kill a maxed 5* with one hit. But she comes a lot closer than Victor.
(All the basic snipers are good. Magni, Lianna and Joon are probably the best of them, but Sartana and Marjana are still good.)
I have both maxed, and kinda regret of victor. He cannot quick kill enemies while sartana is a good and heavy hitter. My vote for sartana
Victor–as long as you’ve been prioritizing a 4* dark mana troop.
He’s a deceptively strong hero, because it’s easy to underestimate the value of the very fast defense increase. He’s a fixture on my top raid and war team.
Dark has a lot of strong 5*s, but I don’t regret giving mats to Victor at all.