Part D Drug Plan providers: Envision vs. SilverScript?

Anyone had any positive or negative experience with either EnvisionRxPlus Silver or SilverScript Choice? I need to switch my Part D drug provider, and these two came up lowest priced.

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Hadn't answered before because my info isn't current. But, for what it is worth, my mom had SilverScript and during the time I was handling her affairs (2009-spring of 2013 when she passed away) I had no problems with the company. Billing was smooth, coverage took care of all of her medications and I don't think I ever had to call them with any sort of issue. Now, Mom was living in an assisted living facility where her prescriptions were filled by a pharmacy they had a contract with, so the facility dealt with the pharmacy which dealt with SilverScript. I saw the monthly billing statments and the periodic reports from SilverScript and there were no problems from what I saw.

Thanks for your input, Cody.