Overview of R versions: CRAN, MRO, and R Server

Wondering just how the different versions of R compare?  And now doubt you have many of these questions:

1. Should I use: 
1. pure open source community supported CRAN version, 
2. enhanced Microsoft R Open, or 
3. R Server
2. Multi-threaded 
1. which R option, if any, supports multi-threading
3. In-memory constraint
1. which R option, if any, supports big data, and breaks out of the in-memory road block

Frank Banin has written up an excellent summary that compares the various R versions currently available. You can find it on SQLServerCentral:  Advanced Analytics with R & SQL: Part I - R Distributions