At this point, Alexa is capable of tens of thousands of different skills, including meditation sessions, games, trivia, white noise, timers, alarms, and more. It can also look things up for you, read you recipes, check your calendar, and control your smart home.
HomePod has Siri, Apple's digital assistant. But Siri on HomePod is not the same as Siri on the iPhone — its abilities are limited, so it can't do things like look something up on the internet or call someone for you.
And Siri, in general, is nowhere near as flexible or as comprehensive as Alexa when it comes to connecting to your various smart-home devices and answering questions.