SugarCRM vs vtiger CRM

SugarCRM is an alternative CRM system that is available in both open source and Commercial open source applications. Sugar's functionality includes sales-force automation, marketing campaigns, customer support, collaboration, Mobile CRM, Social CRM and reporting.
vtiger CRM
vtiger CRM is a community-driven, fully open source, CRM software with a worldwide community of developers and user. It includes modules to manage leads, sales opportunities, quotes, invoices, support tickets, knowledge base, inventory and more.