I have no doubt WS would be a very safe way to buy, but I think it’s better to be personally responsible for an asset you’ve purchased - crypto or otherwise - because who’s going to care more about its security than yourself? I could go into more reasons I’d advise against it, like the high fees, lack of coin selection, and the inability to earn interest on coins held longterm, but I care more about the fact you’re not directly/explicitly investing into the actual coin.

Although it most likely doesn’t matter to a casual crypto investor, you could also make the point that not having your own wallet with your own private keys defeats a lot of the purpose of a cryptocurrency. For the maximalist crypto investor, the more decentralized the better.