Quote Originally Posted by Arcturus View Post
I'd put money down that it doesn't matter. It's random. So you'll definitely get a lot of people saying they only got their 5* toon from using 1 soul instead of 50, but there will be a lot of selection bias. But by all means, do whatever you feel brings you luck!
Exactly this... though personally, my two luckiest pulls (Corrupt General and The Prisoner) were both single soul opens, and both were souls that dropped from secret locations. I know this is only coincidence though. Random randomness...