Neither are going to be the top choice of real audiophiles. The echo has a true woofer which the tap does not. The tap is more for a backyard party. But both should fill the room with music.
In my own experience, the echo is way better at hearing you across the room, and hearing from multiple sides. The tap was designed with the idea that you were going to be pressing a button and therefore you would be within a foot of it when speaking. Although they now have the option to set it to always listening, they didn’t change the microphones when they did so.
And if you do have it set for always listening, the battery life is way reduced. You’re supposed to get nine hours of regular use, but if you set it to always listening, you may only get four or so.
If you absolutely have to have a cordfree device, the tap is certainly worth considering, but I think for most use cases the echo is going to win.