We should make PolyGerrit the default ui for wikimedia gerrit.
It would let new users get use to the new ui (as the old ui is going away very soon upstream possibly in the next couple of weeks or when ever the next release gets branched).
PolyGerrit in 2.15 is mature enough for most users, users can still go back to the old ui (which on the footer has a nice switcher to ease this)