Both engines are reliable.
The key factor with the 140/150PS is it’s flexibility as it has cylinder on demand so you get significantly more power for minimal drop in fuel economy - sometimes more economical as there is no need to work the engine harder. It also gets up to temperature quicker.
The 125 engine is much older tech and IIRC some reports of chain stretch. The 150 has a belt with 5 year replacement recommendation, so factor that into cost.
Trips to the shops - no real difference depending on distance but on a longer run the ease of driving is night and day.
The A3 is a step up in size from the Fiat 500 - is that likely to cause an issue e.g. parking? Bigger car & smaller engine does mean more work.
The A1 of that era is old school Audi build quality - just try lifting the bonnet or boot lid - they are both heavier than those in the A3. The 150PS in the A1 can be a pocket rocket. GF loves hers. Not as much tech as the A3 and do check the A1 boot size is sufficient as it’s pretty small - can’t comment in Fiat 500 boot size.
A3s normally came with a space saver spare vs the can of goo in the A1.
Thanks John, as always
The finer details help swing the choice
It’ll be a little harder to find the right 150PS A1, but long term I think it’s best. The A3 was canned as it’s been deemed too big
The A1 being the latter examples of old school Audi build quality, wider performance envelope and better fuel economy on slightly longer trips, plus as I’ve been told “It looks cute”, it looks like the hunt is on
Will try and find a nice 18 model with that 70mpg rating (I know its a fairytale) despite the £155 Road Tax cost, flat 3 spoke wheel.
The 5 year belt change is worth it, in my opinion, as you then check the car over at the same time & it’ll be cheaper with the water pump on the other side of the lump
Size isn’t an Issue, they used to drive an Altea, Edition 30 and TFSI Leon Cupra’s. Absolute worst case, we’ve all got access to DJAlix to work the aftermarket magic
The 500 has a smaller boot than an A1 so that’s an upgrade here.
So I guess it‘s fair warning that I’ll be posting in the A1 forum sometime soon as I become their amateur mechanic