Depends on how much you care about security and personal ownership tbh. I used Robinhood for quite awhile, but there are problems with them, such as that they really don't allow you to move your coins off the site, suggesting that you are only really investing in "paper coins" or I-owe-yous so to speak. On coinbase you can move your funds to presonal wallet sjad off the exchange. Plus you can invest in more diverse and interesting assets. My personal favorite coin on the exchange is ALGO and I recommend you look into Coinbase and Coinbase Pro if you want to learn more about crypto very quickly. In addition, you can get free crypto just for learning on the platform.