Is a clojure based system going to be better? Maybe, maybe not, depends on a wide variety of factors, but I'd be very curious what their _actual numbers_ are like and what the scaling breakpoints are for them and, at a minimum, their work in this field contributes to a sense of what is possible and what is easy or hard in this space.
That's the important question. Not how much memory java takes up, which is only relevant as a choice after you've added constraints