i'll add my own experience to carrot's here -- the astra is undoubtedly the better car, more roomy, safer, comfortable (well, except the bloody seat*), quicker by far, sounds like a beast, better grip and less roll (i cant get the back end to step out no matter
how hard i try), and probably more economical to boot...... but it's got no personality and aint anywhere near as fun to pootle around in
and with that it also gives you less confidence - power steering and the extra layer of comfort & cushioning removes a lot of the feedback that help you have a bit more "connection" with the road. therefore you're a little more removed from the driving experience and its somehow less enjoyable. think about it - most fun car on the road, probably a caterham... its a tin box on a 1930s design with a motorbike engine and next to no suspension or refinements
in the polo its fairly unsubtle, you can tell what's going on with quite some detail - the steering weighting up as you go into a corner, then becoming light again if you start to overdo it or the road is wet/icy, telling you to ease off, the weight shift if you yo-yo too hard or it's about to tailslide, the nosedive and the balance of knowing whereabouts the wheels are going to lock on heavy braking... the texture of the road surface, every little ridge and bump... etc

no doubt i'll get used to the more subtle feedback in the new car over time and be back on top of the game, but til then, i dont feel anywhere near as "safe" trying to get somewhere anywhere above a grandmotherly saunter, despite the survival chances in a same-speed crash probably being 50% better, as the chance of actually overdoing it at some point and pranging it or sailing into a ditch are higher
besides, the polo is narrower and lighter, you can squeeze through impossible gaps and chuck it around with much abandon, a bit like a four-wheeled four-seat environment-proof bicycle

to which the "new" car is a more like a BMW boxer GT bike.
convinced you yet?
if it wasnt for the more overriding reasons than the ephemeral "driver satisfaction" (the doors, the power, the gears

) i would have stuck with the mk3 til the wheels fell off or i could afford a proper roadster because the feel is so good. even on squishy stock suspension and steel pramwheels with £30 tyres.
* for some reason my legs have severe disagreement with most modern car seats when i have to position my feet into "pedals" position, astra and escorts included, particularly the left - indeed i'm crash-changing to the best of my ability a lot of the time right now. Need to get a cushiony cover... Can't explain why but it's simply not an issue in the ol' polo... instead my back and right shoulder yowk a little instead if i'm sitting more than an hour, which a lumbar-positioned cushion would probably fix.