Your Polo is three years newer and has one of VAG's excellent TDI engines.
However, dynamically the Polo is stodgy and vague next to the Fiesta. VW have a knack of over-assisting controls to the point where there is no feel or consistency and the Polo is one of the worst examples of it. The suspension is sloppy, the damping too soft and I've played arcade games with more realistic steering weighting and feedback.
My 1997 Polo was also a disgrace. Body rust at 6 years old, interior creaks everywhere and constant niggling problems.
VW do appallingly in the customer satisfaction surveys and my Polo showed why. I hope yours is better.
I am just about to buy a fiesta 1400 zetec engined 98 model, black 3 door, has been run for 20k miles with my previous girlfriend without a single problem, I am set to purchase the car for a bargain price as she no longer needs the car, so I am getting a 68k mile example for a song, I test drove the car and its lovely to drive, just what I'm looking for, my current car is a 1990 BMW 325, so as you can imagine the performance difference should be a great deal, but as I borrowed the car a few years back it is a way smoother drive, no eagerness to have me flying off sideways at the slowest of roundabouts, just good old predictable ford handling, one thing I have come to love over the first 7 years of driving ford escorts, Orion's, etc.
I know about the problems these fiestas have with bottom arms etc so have stocked up off ebay with a set for when they finally go, which, as a rule, won't bother me replacing them as I will be able to have a good look around underneath when the time comes