Winning three games at the normal arena is way more effective.
Lets say you play 5 games to win three games at the arena (two loses).
You get around 50 soul stones, one blue card that is equal to 15 soul stones, and 6 more cards.
One of them must be blue card, other probably white. that means 15+25=40 souls at least.
You get at least 115 soul stones for 5 games at versus arena for three wins.
For 5 games at AI battles you get 15*5=75 soul stones.
I just want to give a personal thanks you the author of this post. Very helpfull deck just tried it out before even saw the end of the video, n i got lethal by turn 5. I do have a2 decks which got me to the level 3 so far on versus, but they dont work agaisnt expert. And about solo arenas, i actually ran into bad picks and couldnt even get 3 wins... Thank you once again for your effort