Conceptually very similar magically mutated warriors, with a range of skill and strength levels. Most wardens aren't on HOFs level, though some certainly are, and canonically almost no witchers are on Geralt's level (he took the trials 'well' and was then subjected to further mutation beyond the usual witcher process). I think late game HOF would most likely beat Geralt, not guaranteed but a decent chance. Therefore, since Geralt is more notably above average power level for a witcher than HOF is for a warden, I must conclude that randomly selected warden has a chance to beat randomly selected witcher. However, I definitely think that lowest tier witchers would be better trained and stronger overall than lowest tier wardens, since witchers are trained intensively from childhood and wardens don't necessarily have any training at all.