1f56bc31_ox_vs_App___SharePoint_Dragons__Farm
[0] Efficiency/Performance [Sandbox] Runs on the server farm, but in a dedicated isolated process. The sandbox architecture provides overhead. [Apps] Apps hosted on separate app servers (even cross-domain) or in the cloud may cause considerable overhead. [Farm] 
Very efficient.
SharePoint 2013: What to do? Farm solution vs Sandbox vs App | SharePoint Dragons
Farm