Resident or Resident but not ordinarily resident

I realize I am oversimplifying things somewhat, but it seems that one of the main determinants between being "Resident" vs. "Resident but not Ordinarily Resident" is whether you plan to stay in the UK for 3 or more years.

In my case, I'm not really sure.  I might stay that long, but maybe I won't.  Does choosing one designation over the other have a tax implication?

By the way, I am a dual US/UK citizen, and I moved to the UK In February 2005.

Thanks!

1. Generally speaking being treated as resident but not ordinarily resident in the UK does have advantages, even if you are domiciled within the UK.
2. You'd also want to consider where you are domiciled as this confers tax advantages in most circumstances.
3. The ultimate answer requires specific advice that you won't be able to get directly from this (open) forum.  I'd suggest getting specific tax advice in the UK.