I went for WES for myself, but it is a pain in the ___
The reason is that WES requires FSC documents to be submitted for all candidates who are applying form Pakistan. And the big issue is that they want the documents to be submitted by the board of intermediate education and not by the candidate. I'm in Lahore and I did my FSC from Karachi, so it was a big problem for me.
One of my friend recently got his ECA through IQAS. It was a simple process, Even HEC attestation wasn't required. He just got the signed and sealed envelopes for his Bachelor and Masters degree from his universities and sent those envelopes to IQAS himself (but he wrote FROM address as University's address). NO FSC documents are required for IQAS if you want to get ECA for your Bachelor and Masters degree.
IQAS took 15-20 days only and the cost is same as WES.