The Yaris would likely be the more reliable, but to be honest, buying a 14 year old turbo diesel is likely to be an enormous gamble either way. How reliable either car proves to be is going to be, to a fair degree anyway, determined by how it has been driven, serviced and looked after during the previous 14 years. And you have no real way of finding this out. Yes, the MOT history can provide some pointers, but i'm afraid i really wouldn't be very keen on either. Is there no way you could free up some more funds to get a newer car?, low cost finance, loan or whatever?.

As for MPG, the Panda is an extremely boxy shape, so it is inevitable that it will require more effort to push it along at 70mph than the Yaris. But do bear in mind, it is not the revs which determine how much fuel is being used, but how far down you have to push the throttle.

FIAT Fix It Again Tomorrow.

Yaris.

I may be wrong here, but your initial choices seem to be possibly because they are local cars for sale (seen in the local newspaper?) that fit your budget? Be VERY wary of just limiting yourself to cars locally available as you:

a) cross many potentially decent cars off your list (expanding your search to nearby towns [say up to 25 miles away] would increase that list a lot, and;

b) would set yourself up, especially if you let the seller know (particularly if you live in a small town or village) that you are a local, because they think you won't want to buy from further away and thus won't accept much of a reduction when haggling over price.

If I were you, I'd look round this website, as well as taking the views of other Backroomers, to determine firstly what type of car you need - size, load capacity, performance, handling, comfort, then look at your annual mileage and driving pattern to see what type of engine is appropriate:

i) If you do under 10k miles a year, then its petrol all the way;

ii) 10k-20k it will depend upon if that mileage is mainly made up of motorway or 60mph+ driving or lots of short urban trips from cold. If you know the service and usage history of the car and its done a decent amount of motorway type miles throughout its life, then some diesels may be fine if well looked after, but it is far more of a risk than going the petrol route. Just one moderate fault with a modern diesel (especially those with DPFs) and you've wiped out any savings in fuel and then some - it may be so expensive to repair that you have to scrap it.

iii) Well over 20k miles - you need a diesel, but frankly, if as I suspect, you don't have much of a budget for a newer car, then save up (why did you sell your 306 without sorting out a replacement? Can you get by for a while without a car and use public transport?) for a newer one, or if the miles are mainly commuting and car sharing or public transport isn't a viable solution (short or long term), then perhaps consider moving home or job to suit.

I agree with others here that your best bet on a small budget is for a petrol engined car - its the far safer bet to avoid expensive (and often terminal or write-off [financially] indcuing) problems down the road. That and go for a spec that has the minimum amount of electronic gadgets and gizmos - i.e. a base or lower middle spec car, as long its been well looked after and not had any major or recurring faults.

Why did you part ways with the 306 BTW? No chance (if it wasn't already sold) that you couldn't spend a bit to keep it on the road and save up for a newer car that reliability could be significantly better over the long term?