Yes, both Salesforce Service Cloud and HelpDesk offer a Free Trial.
Salesforce Service Cloud is designed for Large Enterprises, Medium Business and Small Business.
HelpDesk is designed for Large Enterprises, Medium Business and Small Business.
Pricing for Salesforce Service Cloud Starts at $25/user/month when yearly whereas for HelpDesk Starts at $29/User/Month when Billed Yearly.
Some top alternatives to Salesforce Service Cloud includes Zoho Desk, Zendesk Support, ManageEngine ServiceDesk Plus, Freshservice, Freshdesk, LiveAgent, HelpDesk, SysAid, Jitbit Helpdesk, HubSpot Service Hub, Help Scout, UseDesk, LabiDesk, AzureDesk, HESK and BoldDesk.
Some top alternatives to HelpDesk includes Zoho Desk, Zendesk Support, ManageEngine ServiceDesk Plus, Freshservice, Freshdesk, SupportBee, Teamwork Desk, SysAid, Jitbit Helpdesk, Snappy, Helpspot, ReadyDesk, HelpdeskEddy, Help Desk Premier, Support.cc by 500apps and BoldDesk.