Should I purchase ETFs on FSMOne or Interactive Brokers?

I plan to do DCA of about $2000 per month and mainly invest in US ETFs . I might do it in one go or DCA on a weekly basis. Which broker is cheaper for this?
I know that IB has an activity fee per month but I'm not sure if it will be more expensive than FSMOne if I trade on a weekly basis or whether IB/FSMOne has better ETFs with lower withholding tax.