What do you think, more Critical chances or more Multiplier?

I sincerely believe that you are depending too much on POB for some things. Or maybe it's my lack of experience with POB.
Of course, POB tells you how much damage you do, by appearing quite accurately. But that may be different within the game due to factors that POB cannot take into account. For example, the character for which I asked the question uses (or perhaps used) Lightning Trap. Lightning Trap's damage is obviously greater (on paper) than Arc's damage. But if I go to any boss and use both, it's obvious that Arc is more effective.
Why? Because it is better 10 rays hitting together a single monster than 50 balls scattered everywhere, and maybe half of which will never impact the monster. That's why I don't like to use Controlled Destruction. DPS increases, the difference is clear. But if I go inside the game and do tests the thing changes because with controlled destruction I am losing a percentage of critics that allow me (in my case) to do 4 times more damage than normal.

I don't know about you, but I prefer good chances of very high damage to not so good chances of high damage but more constant damage.

As an average, a crit chance gen gives you between 5-10 actual crit chance.

If you have very high crit damage and low chance, then increased crit.

If you have very high crit chance, but low crit damage, you go for crit damage.

Also, in most crit based builds, crit chance is more easy and cheaper to get. The weapon/spell base crit chance is a factor too!!!

There are spells with low crit chance (5%) which will devalue your % crit chance increases, neaning you need to spend a lot more build budget to reach 100%.

Wpeapons are generally easyer to crit cap and in 99% of the cases, you will end up with a crit damage if given the choice.