I can only speak from 1.4 petrol point of view, it's 75hp engine doesn't sound a lot, probably around 65-68hp after 20 years, and more difficult to tune than the diesel ones, but it's only 900kg so reaches 30mph in ~5 sec, hence for city driving, what I do mostly, is really great. The urban fuel consuption is around 40mpg, so not as good as diesel ones, but driving rather short distances it's better as engine warms up faster.
In straight line it can keep up with traffic usually, but on motorway you gotta push it more until reaches 60-70mph, then due the low weight, only with little gas you can keep it there. Taking over only when no cars in fast lane.
If you push it around 3k-4.5k/rpm, like coming out of a long roundabout or joining dual carriageway, the engine sound changes to a deeper tone, like an exhaust valve opens underneath, and that pull actually rather suprising. No it's not superfast, it's just not expected from a rather design & economy car. Steep uphill is the weakest point I reckon, feels like suddenly you lose 10-15hp and need 2-3x gas than you'd think, usually I'm on ~70% gas when climbing 15% uphill to keep up with others, while normally I'm on ~15% gas. Not sure why, maybe the slightly higher sitting position or the oil pressure can't keep up exactly. I say it'd need +25hp and that wouldn't be an issue either, so I rather recommend 1.4 petrol for mostly urban driving and not long distance everyday commutes, I'd done 170miles trips couple of times a year and my A2 did great, but 1.4 diesel is more suitable for that.