ArcGIS Online offers Free Trial, but Atlas Viewer does not.
Atlas Viewer is designed for Large Enterprises, Medium Business and Small Business.
ArcGIS Online is designed for Individuals, Freelancers, Large Enterprises, Medium Business and Small Business.
Pricing details for both Atlas Viewer and ArcGIS Online are unavailable at this time. Contact the respective providers for more information.
Some top alternatives to Atlas Viewer includes CARTO, eSpatial, ArcGIS Online, Mapbox, Maptitude, MyGov, Pinmaps.net, Agile GIS, Mapify and Geoconcept GIS.
Some top alternatives to ArcGIS Online includes CARTO, eSpatial, Maptitude, vMAP, Esri ArcGIS, 21stCenturyGIS, 3-GIS, Agile GIS and Geoconcept GIS.