Agency CRO vs in-house CRO team: comparison, budget split guidance, and when each wins.
In-house teams have deeper context but narrower test exposure (one site, one funnel pattern). Agencies have broader test exposure across many funnels but less context per client. The right structure depends on traffic volume — sites with > 200k monthly sessions typically benefit from in-house teams with agency overflow.
Agency CRO wins when conversion-rate is the binding constraint on revenue — that is, when the site has reasonable traffic but low conversion. Symptom: rising traffic, flat revenue. Diagnosis: conversion bottleneck. Treatment: CRO investment.
in-house CRO team wins when traffic is the binding constraint — that is, when conversion is reasonable but traffic is low. Symptom: high conversion rate, low absolute revenue. Diagnosis: traffic bottleneck. Treatment: in-house CRO team investment.
For most clients running both: depend on which constraint is currently binding. Typical starting blend: 60-70% in-house CRO team investment for traffic + 30-40% CRO for conversion when traffic is the bottleneck; reverse when conversion is. Re-evaluate quarterly as the binding constraint shifts.
Almost always — they compound. The question is the budget split, not the choice.
Start where the binding constraint is. If traffic is low, fix traffic first. If conversion is low, fix conversion first.
Look at the funnel: high traffic + low conversion = CRO bottleneck. Low traffic + high conversion = traffic bottleneck. Both low = both bottlenecks (start with whichever has faster ROI in your context).