Hi: I am convinced that, at the right volume, banh mi can give you higher margin than pho as a dish, with many other operational benefits as well. So my question is, how do I decide whether I should buy banh mi from a bakery or to bake my own. I have good experience working in commercial kitchen (in non-Viet restaurants).
Any input is appreciated.
Unless you have experience with baking bread, you really don't want to bake your own. It looks easy but it's not, and your restaurant volume alone won't support it.
Banh mi can give you better margin than pho, but also banh mi sells better as day part/on-the-go meal item while dinner sale can be much weaker. So you'll want to factor this into your planning. As @ls-nguyen45 mentioned it's unlikely you'll set up your own baking operation, so you're at the mercy of the local bakery. Clearly banh mi having higher margins alone is not enough.
Making Viet-style/French bread at home is fairly easy but from my experience it's not that easy to make in bulk if you haven't done enough time to gain the experience.
In general I advice against making your own Viet-style baguette/banh mi bread unless your concept and business plan really need it and call for it, namely: you need high volume, you have baking experience, you require quality level that other bakery can't provide.
If you're not located in an area with a good banh mi bakery as a source, then this may also be a good reason. However, the other elements should still apply.
Having a good understanding of your own need and the reasons behind it will help you decide what steps to take.