Neither are great PvE toons. Wizards are better though in PvE for non-Epic mobs and easier to level.
For RvR, they are completely different toons. Infiltrators will almost never get a group, unless it is with other stealthers. They deal very high initial DPS, and usually target soft targets if solo (casters). They can kill very quickly and rely on surprise because of their stealther.
Wizards are almost never solo unless played by a very experienced player, and even for them, the soloing would be frustrating. They rely on groups, and bring groups very good DPS, but not much in the way of utility. Damage is about all they bring, unless you spec earth.
It is a very strange comparison you bring here, in that the people that play infs are normally not people that would play a wizard.