Have you considered mediation? Do you have the willingness to be overt that this distinction in intent has risks for BOTH of you? Not the product and what happens: the risk here is your ability to be mutually respectful as co-founders.
As an aside, speaking as a user I totally do NOT like being shown the free and only told 2-3 months down the track "here's the pay model to get the bits you need" -If you know how to monetize now, I personally think you should launch now with free and paid or at least expose what paid will be, by intent. That page of the options available in each model as a table with tick and cross marks, as a minimum.
That's just my UX input. The above point about risk between you as founders, is what I think your central problem is.
Most importantly, investors do not think alike. You are actually choosing kinds of investors when you choose your GTM.
If you have the option to go free first, you can focus on being sticky.
If you do both, you can focus on conversions.
Generally in a strategy conflict you need to discuss the context level first.
So model it out & discuss - what matters more for our success, conversions or retention?
You’ll be wrong most likely, whatever you decide, but it will give you a HUD to guide your future decisions with.
Common startup experience:
“Retention matters more because X” Turns out X doesn’t matter 18 months later you’ve crushed adoption but now can’t retain “Retention is what we’ve got to focus on” But then your Board helps you attract capital on growth alone
And so on
The point is - strategy is a steering wheel.
Reality, the version happening right now, is the road.