The Ace without a doubt, although you might look at the 350 because of the DD coil. The Ace is very sensitive , so be prepared to dig up tiny pieces. You can also accessorize it with many different coils, an arm shaft extension, environmental cover (highly recommended), and a Sun Ray probe if you so choose. The Delta is lighter, but the Ace is a really great little machine. To me, it's one of the best park hunters around.