The verdict
There is no universal winner here, only a question about your stage. If you are a lean B2B founder who has not yet turned on serious ad spend, Leadpages wins on the maths that matters: 10 USD/mo, a free tier to test live, and an AI generator that gets a lead-capture page published the same afternoon. You de-risk the build and keep cash for the actual experiment.
The moment paid traffic becomes a real line item, the calculation flips. Instapage is purpose-built for post-click optimisation, and its server-side A/B testing and ad-to-page personalisation turn a small conversion lift into more money than the 79 USD/mo it costs. At that point its depth is the bargain, not the expense.
So: start on Leadpages, move to Instapage when your ad budget makes a percentage point of conversion worth more than the subscription. Choose for the stage you are in, not the one you hope to reach.