There is a great differences among these products specially in their stacks/ technologies.
SAP All-in-One:It is based on the same stack like SAP ERP (JAVA, ABAP, SAP NW), It is a 3-tier stack. It is supported more that 500 employees. A1 is bugs free and has more guarantee.
SAP Business One: It is more Microsoft oriented i.e. COM API’s, MS SQL Server. It is a 2-tier stack. Sap Business One supported upto 250 employees. SAP B1 has all the functions required by small companies (advanced SMB). SAP B1 is a software that was bought over by SAP.
SAP R/3: It is large companies. R3 is SAP Product and it has also undergone various re-engineering over time. Example: SAP ECC.. SAP R/3 is based on a 3-tier/n-tier client/server architecture.
I can say “R/3 is Better than A1 and A1 is Better than B1”.
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