I have a 1.9 tdi Altea, it was crap until remapped.
The majority, if not all, mk5 1.9's won't have a DPF however do have known flywheel and turbo problems.
If you go for the diesel, look at a 6speed version.
With your mileage the 1.6 will be good for pottering about with less expensive things to go wrong. You do almost no mileage to justify a diesel.
I recently sold my 2.0 tdi as I did only 3000 miles last year in it.