This idea that F, H, And L preference shares are different than the others conflicts with what all RBS representatives have told me... repeatedly. RBS reps say they can't pay any of the preference shares without paying all of them. Call RBS and ask them.
If you find out otherwise, I'd like to know.
While there might be some language difference in the prospectuses(sp), I think there is also language that makes all subordinated tier 2 debt pari pasu (sp).
This is an all or nothing deal as I understand -- and generally the pricing supports that.
On the other hand, there is an equally good (or unlikely) argument to be made that the class R, S and T shares are the safest as various lawsuits are alleging that RBS and the underwriters knew that market conditions were deteriorating before they tendered these shares. So RBS might redeem these first to get away from the litigation.
Both these claims are probably just fodder for the blogosphere. IMHO, the only real difference betwen classes is yield.