The comparison is slightly misleading as usually phrased, because a SIPP is not an alternative to a personal pension. It is one type of personal pension. GOV.UK lists self invested personal pensions among the types of personal pension, alongside stakeholder pensions, and the tax rules that matter are the same for both.
What is identical between them
The tax treatment does not change. The same annual allowance applies across all your pensions, relief on your own contributions is limited in the same way, the tax free lump sum works the same, and the age at which money can be taken is the same. Both are defined contribution arrangements, so what you eventually get depends on what went in and how the investments performed, rather than on a formula tied to salary and service. If you are comparing them on tax, there is nothing to compare.
What actually differs
The investment range and who chooses it. A standard personal pension or a stakeholder offers a limited menu, often a default fund most members never leave, and it is built to be simple. A SIPP widens the choice substantially, up to commercial property and unlisted assets in a full version, and hands the decisions to you. That is the trade: more control and more responsibility, at a higher annual cost, whether or not the extra freedom is used.
Stakeholder pensions sit at the simple end
GOV.UK notes that stakeholder pensions must meet specific government requirements, including limits on charges. That capped, standardised design is the opposite end of the same spectrum from a full SIPP, and for someone who does not want to make investment decisions it is a reasonable place to be rather than a lesser product. Cost and simplicity are real features, and paying for freedom nobody uses is the most common mistake in this comparison.
Which suits whom
If you will hold a couple of funds and never look again, the wider permissions of a SIPP cost money and deliver nothing. If you want to hold commercial property, run a portfolio yourself or consolidate several pensions into one place with a wide choice, the SIPP earns its charge. This site does not make that recommendation for you, because it depends on facts it does not hold, and a personal recommendation is a regulated activity performed by authorised firms.
Questions people ask about personal pension vs SIPP
Is a SIPP a personal pension?
Yes. GOV.UK lists self invested personal pensions as one type of personal pension, alongside stakeholder pensions. They are not competing products; the SIPP is the version with a wider investment range and correspondingly more responsibility on you.
Does a SIPP get better tax treatment?
No. The annual allowance, the limit of relief to your earnings, the tax free lump sum and the minimum access age are the same across personal pensions. If tax is the reason for choosing between them, there is no difference to find.
Is a SIPP more expensive?
Usually, because the wider permissions and the dealing facilities cost more to provide, and the charge applies whether or not you use them. Whether that is worth paying depends entirely on what you intend to hold in it.
What is a stakeholder pension?
A personal pension that must meet government requirements including limits on charges, which makes it simple and capped by design. It sits at the opposite end of the same spectrum from a full SIPP and suits someone who does not want to make investment decisions.