Differences Between Infopackage Groups and Process chains

Info Package Groups:  used to group only Infopackages where as Process chains are used to automate all the processes.
Infopackage goups: Use to group all relevent infopackages in a group, (Automation of a group of infopackages only for dataload). Possible to Sequence the load in order.
Process Chains :Used to automate all the processes including Dataload and all Administrative Tasks like indices creation deletion, Cube compression etc
Highly controlled dataloading.
InfoPackage Groups/Event Chains are older methods of scheduling/automation. Process Chains are newer and provide more capabilities. We can use ABAP programs and lot of additional features like ODS activation and sending emails to users based on success or failure of data loads.