cloud based esign products pros and cons

I have a client who is looking for the ability to esign fillable pdf contracts. They want to ensure privacy and security of their customers data input into these pdf files. I was looking at Docusign or Echo/Esign by Adobe. They would transact less that 100 documents a year. Would be very convenient but not necessary to be able to fill out and esign on mobile as well.

Any experience, or pros and cons you can share.... any other products that have a secure cloud environment in which to do this esigning?

Thanks,