Bro! Trust me i have been in the same dilemma and i could not choose between either.
All i did was read two rakat " Salat e Hajaat" and then leave it to Allah...
Although i was determined to go with CES but then i got inclined towards ICAS and finally sent my docs to ICAS
CES Vs ICAS:
CES has a lot of manual work ( for e.g. the credit card form has to be filled out instead of online)
CES has no online profile ( you have to fill out the application)
CES requires that the university send the sealed envelopes to them directy ( which is a hassle)
With ICAS:
You create an online profile, Pay you fees through CC , get an ICAS file number is email.
Make photocopy of your degree and transcript.
Enclose the sealed envelope from HEC ( if you have one)
Enclose the document form sent in email by ICAS
FInally mail your application.
I found ICAS easier.
Lets see when i get my ECA...Fingers crossed and time running out.
Pray for me
JazakAllah