Most women's ERG leads inherit a company channel, a shared spreadsheet and a People team survey, so the real question is which of those ERGCircle should replace and which it should sit beside.
Nobody buys ERG software the way a company buys payroll. You already have a channel where the chapter talks, a spreadsheet where the budget lives, and a company survey somebody else owns. ERGCircle only earns its place if it holds the three things those tools keep dropping: who actually walked into the room, what the program spent against the approved lines, and what the year added up to in a form an executive sponsor will read without a translation.
The three comparisons below are written as fit questions rather than scorecards. Each one names what the other product is built to do well, where a women's network with a modest budget and a volunteer core team runs into its edges, and which kind of ERG lead should simply stay where she is. If your chapter runs four events a year and files no report to anyone, the honest answer is often the spreadsheet you already have.