All right then, a reply in short.
Basics:
- a stakeholder pension is just an investment account, and if you agree that the life companies are not scouring the world trying to make you money, but simply investing where you tell them to, then the only measures of value are the charges you pay for them doing so, the taxes you save/pay and will pay, and whether you can invest in the markets you want to. The same reasoning applies to your UK auto enrolment pension, by the way.
- in terms of charges, stakeholders should have been averagely expensive (Sandler) but turned out not to be. However for accounts of less than 30k, about the best you can do. Unless of course you have not brought all your pensions together
- in terms of tax, a UK pension is still tax efficient from a US/UK national in the UK, but so is a US pension account. In fact, if you can work the option (not so easy), the US account is more tax efficient than the UK one both in accumulation and in depletion (pay out). Assuming that is, you are resident in the UK when you take an income. If you will be resident in other countries, the above may not be true. Also, you would not believe the tangles that US companies get into when they realise you are not US resident. Actually,you probably would,
- the big trouble with stakeholders is that you can't invest where you want to (where the growth is).
Summary
UK Stakeholders are ok as a start, until you get enough in the account to get an optimal return from world markets. While you're accumulating that, invest safely. When you get enough move it all into a SIP. To figure out the best would need a lot more information from you.
If I were you, I would work out a strategy of how to maximise both UK and US state pensions first. They're better value.
I can give you a shortlist of three companies to advise you, probably 1000 to 2500 GBP.
If I wrote a book on this, priced, say £15, would you buy it? Is there a market for it?