Which will perform better, the NS&I 5 year RPI bond, or Postfinance e-deposito account with 1% interest (consider only pre-tax performance for simplicity).

To be measured 5 years from 1.7.2011
FX exchange rates for comparison to be taken from oanda.com day average.

would also be interested in hearing your reasoning.

Lines in the sand and all that... We're taking some directions here!

On the RPI side for someone investing on the first of july the index level is that of May. If anyone can find it on the ONS site please post it here as i'm on the IPhone and it's a pain!

I think that if after five years (if we're still around) and the result is tight we should take into consideration the tax rate.
Since the 0.5% aer is actually equivalent to 0.63% for the basic rate tax payer and 0.83% for a higher rate tax payer. For the post-finance account to really outperform the rpi certificate the pound has to go down by more than inflation year on year for the next five years...

Somehow I really don't see that happening...

tax is ignored. in any case, you should pay the same swiss tax on both.