AMP is a performance framework, but is it worth it? You could just take Google's word that it is, and that would be enough for some people. But if you're curious, you can measure the performance of your AMP and non-AMP pages. Depending on how well-built your original page is, you can expect to see performance gains in your AMP pages. And even if your non-AMP page is already fast-loading, you should still see improvements when it's served from the AMP cache.
Measuring web performance is a whole subject in itself, with a wide range of dimensions to measure and tools to measure them. We can only scratch the surface here, but it will be enough for you to do basic performance measurement of your web pages.