There is a lot of things around the answer.
As @FPoPP said, "one handed weapon tend to have less attack than two handed", but of course this depends on the required level for the weapon. Important to mention that Two handed swords usually has 3 Imbuement Slots and One handed has 2.
The best weapon depends on the options you have, i'll explain with Swords.
Cobra Sword (Lv 220, One handed) vs. Slayer of Destruction (Lv 200, two-handed) Same element: physical. Both of them have atk:52 but, Slayer of Destruction offers you 3 imbuement slots and Cobra Sword only 2. So if you are hunting alone, the best option is Slayer of Destruction because with its 3 imbuement slots (mana, life, crit) and equiping an armor with life leech, you will gain a lot of HP.
Gnome Sword (Lv 250, One handed) Element: Energy. This sword has 10+42energy atk, but it is the only sword that deals energy damage so in this case there is no other option.
Naga Sword (Lv 300, one handed, atk 8+44 ice) vs. Soulshredder (Lv 400, two handed, atk 10+47ice). This comparation is a little fool because Soul items are BiS but, it doesn't mean that Naga Sword doesn't worth. In this case, you want to use naga sword when you need the elemental protection of any shield. Once you are fine without that elemental protection go with two-handed.
If you want to make your own comparations with the weapons you use, you can open the Market and in the upper left menu select "Weapon: axe/sword/club", there you will see all the axes/clubs/swords in game and you can click on the "Level" button to see only the ones you can equip and finally click on the "Details" button to see the stats.