Problem with 4AFE is you must make sure its a japanese engine and not local civil engine out of stolen 1.6 GLI. Pathans will say 5A and 4A both are 1600cc though 5A is 1500 ad 4A is 1600.
I am using 5a and found it to be good enough for some one like me who likes to stay in fast lane and likes good pick up with light foot.
When you decide to swap any engine look at my thread it will help you a lot.
5EFE got good low end torque and 5AFE little better torque but at bit higher rpm.
Low end torque helps you in city driving like when you need to go from zero to 80 . But 5EFE are not easy to find and pathan might sell you 4EFE if you dont have your eyes open as 5EFE. Because they dont differ between 4E and 5E and there price is also same.
IF you want to run your car on CNG make sure you dont buy a engine with DIS (Distributor Less Ignition) and buy one with distributor. 5E comes with DIS and distributor one.
It will be hard to find Clean 5EFE and not that hard to find 5AFE.