Salary Sacrifice by Umbrella or pay into SIPP myself?

[bbp]

First time contributing to pensions. It's still hazy for me. So, please tell me if I got this right.

If my umbrella pays into my SIPP, I'm saving on the employers NI and reduced taxable income, but won't receive any tax reliefs.

If I pay this myself from the net pay, I'm paying more taxes upfront but can access tax reliefs.

Is one way always better than the other?

[eek]

Salary sacrifice means your pension pot rather than HMRC receives the NI money (13.8% employer NI and 2% employee NI).