Wow - I hadn't seen this product before! Thanks for sharing.
I'm currently running a cobbled together "stack" on my solar site https://sunboxlabs.com (Hugo, Paypal, NetlifyCMS, custom JS for coupon and affiliate codes) and have been refusing to move to Shopify.
Maybe I'll give one of these two a shot. 3% on top of the CC processing fees is not too bad. But not great either for a $599 product...
Their framing it as a refusal is interesting. As someone who works for an E-commerce consulting agency, we do a lot of Shopify and WooCommerce work and generally there are valid reasons for each. The biggest reason to stay _away_ from Shopify, is if you want absolute control over everything. If you can jive with their checkout flow (which honestly is great), then there's not too much that their third party add-ons cannot somewhat incorporate.
The other big show-stopper from our experience is multi-lingual support, but tbh that sucks on 95% of ecommerce platforms.
That being said, maybe it's because Vercel already made a Next.js Commerce product: https://nextjs.org/commerce