is there a technical comparison between digi wr44r and cisco c819 ?
I’m not aware of any. However you can compare their respective spec sheets.
cisco:
http://www.cisco.com/en/US/prod/collateral/routers/ps10906/ps380/ps11615/data_sheet_c78-678459.html
Digi transport:
http://www.digi.com/products/wireless-routers-gateways/enterprise-routers-vpn-concentrators/transportwrfamily#specs