Shield, Block Chance value

assuming i have a shield with 33 % block and various stats and a similar shield slightly or mildly better stats but only 30 %, which one would you use ?
I am under the Impression that block Chance is very important on a shield and outweights minor life/resists. Is that correct ?

Yep, its easier to get resists like block chance (not counting spellblock what is another big reason).

Depends.

If you're going for high block chance then every % block is good to have, more than resists, as you can get those elsewhere.

I wouldn't recommend using a shield without 50+ life (unless it's Aegis Aurora) even if it had 5% more block chance.

If you don't intend to invest passives into block chance, then don't do it on the shield either, take life and resists and get DPS elsewhere.

Block chance becomes more valuable the more you have. Going from 30% to 33% block change means you get hit 67% instead of 70% of the time. That's a 4.3% improvement.

Going from 72% to 75% block chance means you get hit 25% of the time instead of 28% - that's a 10.7% improvement.

Usually, best improvments are, if you going for ~55 or full block; ~55% block will double your EHP against everything the first time, while going from 50 ->75% doubles your EHP again. 20k EHP with 5k flat life is _really_ tanky already.

What's EHP?

^ Effective hitpoints (health points)

Example (EHP vs cold damage):
HP: 1000
Resist Cold: 50%
Someone attacking you with cold damage
He need to do 2000 damage to kill you
So EHP: 2000

If there is some defense percentual based (0~100%) then EHP grows exponencial.
Resist Cold 85%
He need to do 6666 damage to kill you = So EHP: 6666

Resist Cold 99%
He need to do 100000 damage to kill you ...

Every defense mechanic can be somehow calculated into EHP.

If for your not speccing block, don't worry about your block.