3rd pillar, permit B and withholding tax

Let's make an important premise:
The Swiss pension system is designed to reach retirement with about 60 percent of final salary, but only those with full contributions can get close to this percentage.
That said, those with a b permit generally came to Switzerland after their studies or at an older age, and therefore will have an even lower pension than someone who has made full contributions.
So it becomes clear that in order to have a better pension, the third pillar is crucial, beyond whether you do 3a or 3b.

The main difference between Pillar 3a and 3b lies in the tax treatment.
Pillar 3a can be deducted from taxable income, while Pillar 3b cannot.
To take advantage of the tax advantage offered by Pillar 3a, those who have a B permit and are taxed at source (with a salary of less than CHF 120k), must apply for additional ordinary taxation and thus deduct the premium paid to Pillar 3a.
The benefit that can be obtained depends on several factors: 
On the canton of residence: each canton applies its own withholding tax rates. 
From the taxable income: the higher the income, the higher the taxes and therefore the cheaper Pillar 3a becomes.
From family situation: for withholding tax, it makes a big difference to be single or have family.
From how much you want to pay into Pillar 3a: the more you pay into Pillar 3a, the greater the tax advantage will be.
By evaluating all these factors, one can figure out whether it is worthwhile to make a pillar 3a, tying up the capital until retirement, or a pillar 3b and have the freedom to withdraw it early. 
For this reason, competent advice is essential