The Radisson Blu Waterfront is among the nicest Radisson Blu properties I've visited, so unless the Park Inn (which I haven't been to) is extraordinary nice, yes the Radisson Blu is substantially better (remember the brand hierarchy is Park Inn < Park Plaza < Radisson < Radisson Blu).

FWIW, I've usually received an upgrade to a (partial) sea view room as a Gold member, though that was usually during off-season. I've actually frequently seen this hotel being fully booked.