Paladin use 2 Lay on hands to use Channel energy, but how much does he cure? The channel suppose to be as a cleric but then does this means it heals more than lay on hands? Because a Paladin Lv 5 only have 2d6 lay on hands while a cleric 5 have 3d6 channel. Or does the paladin channel heals the same amount of dices lay on hands does?
I think that it does do 3d6 in healing.
The main draw of LoH is the ability to do it to yourself as a swift action.
Paladin use 2 Lay on hands to use Channel energy, but how much does he cure? The channel suppose to be as a cleric but then does this means it heals more than lay on hands? Because a Paladin Lv 5 only have 2d6 lay on hands while a cleric 5 have 3d6 channel. Or does the paladin channel heals the same amount of dices lay on hands does?
At level 5, a paladin lays on hands for 2d6 healing, as you said, BUT adds his/her Charisma modifier to this, which you neglected to mention.
If your paladin has a 16 or higher Charisma (and he should), that's 2d6+3 vs. 3d6 ... so a potential 5-15 healing instead of 3-18. Once that Charisma's around 20, that +5 will really pay off for those times when you channel and roll mostly 1s and 2s.
Lastly, channel bursts heal everyone within the radius, unless you spent a feat on Selective Channeling. Lay on Hands is never going to heal anyone other than the person you want (or harm the undead you want).
And as mentioned, the ability to swift lay on hands yourself ... pretty nice.
The other advantages of Lay on Hands is you can use a Mercy.
Also, if there is only one person needing healing, Lay on Hands provides more healing per use, since it only consumes one use.