Pros
I don't see any pros in this staffing company. Getting your money on time is the most basic requirement from any company and Stansource does not offer even that.
Cons
Many benefits mentioned on their website (and explained to you while doing H1) simply do not exist - such as
1) The payment is net 30 (not net 15 as told)
2) There is no direct deposit
3) No health insurance
4) They do have bunch of sales folks sitting in India but they do not know much about US market
To add to that - Payroll is never run on time. No one would respond back to your emails, if you follow up. Simple requests like providing Paystub are also ignored.
If you want your peace of mind, better stay away from this company