Install Battery Monitor Widget, and you will see how much current each option gives at different levels of charge.
To be exact, the device DRAWS current, it's not a question of the highest output being the best. If the device can't receive more juice, the additional output cannot be used.
When the battery is nearly empty you will see the biggest current draw - as the charge gets closer to 100%, the amount the device draws drops, until it reaches 0mAh on full charge.
My OEM wall charger provides up to 1000mAh, and the PC USB provides 500mAh, you will initially charge the device faster with the wall charger, until the current drawn by the device drops beneath 500mAh - after which point they will charge equally fast.
That, in the case of my phone (with a Mugen 1500mAh battery) happens around the 60% charge mark. So if the charger outputs are as mentioned above, you wouldn't see any difference in the rate of charging after 60%