I'll bite although there's many factors for different builds in the specific two you've listed I would say warriors are more general purpose and wyches more role specific.
Hard to say which is better value because it depends but I would lean towards warriors simply due to their ranged presence. The addition or absence of 20 splinter rifles will be felt over the course of a game.
I feel wyches are straight better when faced with opposing disruption elements in your face, specifically dreadnoughts and MCs due to haywire and 4+ dodge-duck-dive-and-dodge save. Such units will rampage through a backfield full of warriors but can be tied up or even destroyed by a unit of wyches.
Warriors are IMO better in general simply because they bring ranged weaponry that gives the option the shoot from cover, force grounding tests for FMCs and have 5+ armour for explodes tests although this last doesn't matter all that much. It can be argued that wyches can also shoot and it'd true but obviously far less effectively.
Either choice gets better in multiples with wyches really benefiting from multiple units due to saturation and the deadliness of hwg's vs Mech. To this point I'm more familiar and comfortable with warriors using wyches for the roles mentioned above.