Single-handed giver’s weapons have +10% condition duration.
Giver’s two-handed weapons only have 10% condition duration as well.
However, looking at Anet’s patterns regarding two-handed weapons, where prefix stats are usually (just about) doubled from their single-handed counterparts, it would seem that Giver’s two-handed weapons should have +18% (or +19%) condition duration.
For example, the Berserker’s prefix gives +5% critical damage to single-handed weapons while it gives +9% critical damage to two-handed weapons.