Even as a Volkswagen fan (and previously VW driver), I wouldn't recommend the Polo GT. People already said why, parts are expensive and you spend a lot of the money on the brand, not the actual quality of the car. Not good when budget is limited.
I would go for the Toyota Corolla, the brand is reliable and the car has been build in such great numbers that parts tend to be cheap and always available.
Also, don't let yourself get fooled into buying a small car (like the ones chosen by you) in a "sport configuration" like the Polo GT. Keep in mind that the manufacturers still have to make them cheap, so they mostly aren't that "sporty" or tend to have a high wearout. IMO it's better to have a basic running/reliable engine and some extras in the car (like AC, good radio system, good seats etc.) than a "fast" car with no extras/comfort at all.
(Side story: A friend of mine drove a modified Polo with large chrome rims and an after-market racing chassis suspension. Every trip above 5 km was a REAL pain in the ass. Literally.)
Edit: Also, if you have a "car friend" take him with you to look at the car. Or when having chosen one, bring it into a shop and let them make a check-up. There are a lot of scammers out there who sell cars with broken motor blocks or near-death transmissions.
