The short answer is, the DCI is massively more economical but costs a lot more to fix when they go wrong, effectively writes the car off when/if it fails. - But it may go for 10 years and 100k without failing! but they are getting old now.
1.4 16v will probably do 40-45mpg in comparison to 60-70mpg in the dci, but they dont cost anywhere near as much when they fail and they are fairly reliable.
In terms of performance, it depends how you look at it, both are adequate to drive around in, a DCi 80 or 100hp will most likely feel faster than the 1.4 due to the torque but the reality is the 1.4 is probably the fastest of the bunch in a drag race, but of course a drag race isn't reflective of a real word scenario!
For me, after years and years of being a big DCI head, id say the 1.4 16v as the DCI's are just getting too old now, unless your good with spanners then id consider either to be a good choice