Modern Warfare Reflex is a lot better than The Conduit.
The single player campaigns both have frame rate drops but on the whole Reflex is stronger and more engaging imo.
The graphics are better in bits of The Conduit but again Reflex comes out on top because it is more consistant due to better design.
The games really concentrate on online play though. The Conduit does have Wii Speak support and allows for more players online but those features are cancelled out by Reflex having better maps, no annoying bugs and more match types.