okay one thing that has troubled ford passenger cars (except their trucks/pickups) is the terrible RV and expensive parts.
fiesta has over the years proven to be a successful car and thus RV for this model is considered good for a ford.
however, expensive parts is still a problem especially if you buy it from ford auto connexion (FAC).
but i think fiesta has the critical mass for stockist to import oem/compatible parts from overseas at a cheaper price than from FAC.
one of the biggest stockist is Vanli, do check them out and see if the parts are within your comfortable range before deciding.
things like oil filter, air filter, etc. are common stuff and won't be expensive look for things like absorbers and mountings those can be a cheap rm100 a pair or crazy rm1000 a pair.

i10 iinm is a korean b-segment hatch so upgrading to a fiesta won't be that much better.
of course cars are fiesta/city are at the top range for b-segment cars being the more technologically sophisticated and high-spec.
so what is the difference?

let me put it to you this way....it is like the difference between having a steak at a hawker center vs having a steak at a 5 star hotel. a steak is a steak nonetheless but a hotel gives you a better quality one, fresher, non-frozen, more juicy, more tender, etc.....while the hawker center will probably just buy any cheap cut from the market or frozen food section of the supermarket.

so yes there is an upgrade even within the same segment but maybe with your budget you can consider something a class higher?

altis/sylphy/civic are good choices for a used c-segmemnt within your budget, i would say it is an ideal budget as you can choose cars that are of better value, lower mileage and not so old especially for Civic since it has good RV.

Altis/Sylphy the newest and the one before it share everything in common so you don't have to worry about parts being expensive or their availability.

The current and previous Civic do have some differences. Long story short only the previous generation FD2 (2000cc model) is worth to get, it has better equipment and mechanical parts. The current and previous 1800cc model is very similar to each other they both use the R-series engine.
The current 2000cc model also uses an R-series engine, so no more DOHC i-VTEC it is SOHC i-VTEC with the R-series.
However, if you crave for power you can always install the Turbo kit