Wired is "orders of magnitude" less laggy' than wireless. This is fact.
Wireless can "feel" less laggy if the poll rate is extremely high, such as the G700 Mouse, however the high poll rate kills the battery quite quickly.
As far as keyboard goes, You definitely do NOT want wireless, because there are currently NO keyboards that poll higher than 125hz standard usb rate, over wireless. And the usb rate override rate change drivers don't work on wireless keyboards, because it has to be setup to transmit at higher than 125hz, which can only be don't by the manufacturer.