I am round the corner in Double Bay and yes, exposed to a (North) Easterly. Flip side sheltered from a SW. I would say the downside of Parsley would be the parking. At the weekend you would be up on the road and have to walk down to the park. The waiting lists don't look too bad, Im surprised. Cant think where the nearest tender rack would be if that's how you access your boat.
I dont moor there, but do travel up there regularly to stop off at Brooklyn. It is a little open to an Easterly, but much more to a Southerly as it sweeps up the Hawkesbury from the Cowan Junction. But the waves don't get too big, it is more wind against current. But you will notice than no houseboats are moored there. Nice muddy bottom tho, your mooring is not going to move anywhere.