The title is the same. The days are not.
In-house at a startup
You will do everything: sourcing, calls, scope, launch, QBRs. You will fight for engineering. You will learn judgment because nobody else will make the call. The risk is becoming the person who “does partners” with no power to ship. Ask in the interview who owns the integration roadmap.
In-house at a platform
Salesforce, HubSpot, Shopify, a cloud. You will learn programs, tiers, review checklists, and how a giant partner manager is measured. You will see more volume. You may not ship a whole motion yourself. Good for learning the other side of the table. Less good if you want to own a P&L in year one.
Agency / studio (like PartnerMatch)
You will run the motion across several products. You will see more patterns faster: the same discovery failure, the same bad commercial, the same silent launch. You will not own the brand. You will be measured on whether the partnership actually ships for the client.
How to choose
If you have never shipped a partnership, a startup or a studio where you can own one end to end is the better classroom. If you already shipped and want distribution literacy, a platform program team teaches you how the big machines work.
Do not pick based on which brand your relatives recognize. Pick based on whether you will leave year one with a case you can write in one page.