it really depends on the purpose of use. I believe siri and cortana have same functions, not as good as alexa.
number one voice assistant is still amazon" product
best audio experience should go to homepod due to its speakers.
of course, detachable would be the best, if it can hold the same powerfulness and battery life.
there is a compromise.
right now, convertible is not so great, it's not light weight enough.