For me, i was using WES just because everyone was going for that, also as it uses World in its name
means no logical reason behind that.
Offcourse if you are time conscious then you should go for WES, but as other mentioned, struggling with BISE/IBCC/HEC etc can also take these 5 weeks.
Also WES is little bit strict for their secondary education requirement and very very very bad in email and phone response.
Thats the reason I finally going for CES, i found that there response time is very high, you get email response in minutes and they can reply your queries. While WES replied me after one week, and the reply of my detailed question was that "Please review our document requirements for your specific country, You must follow those specific instructions", and there was no response to my actual question.