First off, Associate of (ISC)2 is a designation that can be obtained for any of the (ISC)2 certifications. It means that you have passed the exam but can not satisfy the certification requirements at the time of passing the exam. From there, you have 3 years to meet those requirements. In most cases this would be the required years of experience.
Your choice between CISSP and SSCP is a totally different conundrum. It largely depends on where you see yourself evolve over the next few years. Where CISSP is targeted at the generalist security practitioner that touches all aspects of the business (from management to technical), the SSCP is meant for the more hands-on practitioner.
It should not be a question of which one you can get faster but more a question of where you see yourself evolve throughout your career.
I hope this helps.
Sic semper tyrannis.