LawConnect won from Comanche last year by just 51 seconds in a thrilling finale after a treacherous 628 nautical mile slog with the two 100-footers again set to battle for line honours.
Two other supermaxis are entered -- Wild Thing and Maritimo -- among a fleet of 105.
The big boats are predicted to get off to a flying start from Sydney Harbour on Boxing Day before they head down Australia's east coast then tackle the notorious Bass Strait towards the Tasmanian state capital Hobart.
Comanche navigator Juan Villa is confident of a fast race if the long-range forecast of north-easterly winds holds.
"In our mind is whether the conditions will lead to possibly break a record," said the Spaniard, who added that depending on what the weather does "we feel that our boat is quite, quite strong".
Weather is a critical factor in the race, which was first held in 1945, with winds often shifting rapidly in direction and intensity.
In 1998, when a deep depression exploded over the fleet in the Bass Strait, six men died, five boats sank and 55 sailors were rescued
"There's a lot of sections through the race and a lot of weather phenomena that can affect the strategies," said Villa.
"It's a really exciting race. It's really complicated, but that's why it makes it very interesting for navigators."
Four-time champion Comanche is the current race record holder after it surged over the finish line in one day, 9 hours, 15 minutes and 24 seconds to set a new mark in 2017.
Alive, last year's overall winner of the Tattersall Cup, which takes into account boat size and other factors, is back to defend its title.
Other previous overall winners in the fleet include Centennial 7 (formally Celestial), Love and War and Unicoin, which won as Assassin.
Love and War, a three-time winner, is being skippered for the first time by Simon Kurts, son of owner Phillip Kurts.
"We're absolutely capable of winning the race. The tougher the race is, the better we'll go," said Simon Kurts.
There are six international competitors including French yacht Cocody, Poulpito from New Caledonia and the Hong Kong-based Antipodes.
The Filipino-crewed Centennial 7, Caro from New Zealand and American challenger Bacchanal are also entered.
Maritimo Katwinchar, built in 1904, will become the oldest boat in the ocean race's 79-year history when it sets sail, co-skippered by 45-time Sydney-Hobart veteran Michael Spies.
Kismet, launched in 1955, is the second oldest and at 9.3 metres the smallest, with 32-time race veteran Sean Langman at the helm.
The number of women taking part continues to rise. Apart from those crewing, there are 16 female owners or skippers/co-skippers.
