I have both cultus ags 2018 and swift auto 2018 being used within my family. Also used swift 1.3 dlx 2012 for 5 years. I have driven them almost daily and i prefer cultus over swift anyday
Cultus > swift
Mileage wise
Softer suspension
Less cabin noise ( khar khar choo choo)
Life time token
Can be bought by non filer as well
Ags better than simple automatic
Smoother drive
Swift > cultus
Instant acceleration(manual)
Feels more stable
Better for long journeys
Navigation system
Better AC
Some people have reported issues with control arms of their cultus ( well idk whats that, but some senior pakwheelers reported having issues with their cultus, no such issue in mine till now Alhumdulilah, 20k driven bought in april 2018.
Well these are just my opinions others may add to it.
If i were in your place i'd go for cultus and preferably ags.