I've been running split tests between fully automated sequences and manual, personalised outreach for a couple of quarters now. The results are pretty clear: automation crushes it on volume, but human-led stuff wins on reply rates and actual deal progression. The trap is thinking it has to be all or nothing.
A colleague pointed out that the real win is blending both - automate the boring parts (scheduling, follow-ups, basic templates) but keep the human in the loop for positioning and approval. They set up their system with their ICP's real problems baked in, plus a few past emails that actually converted (with context why), then act as the approver early on. That way you catch drift, refine as you go, and eventually you get close to full automation without losing quality control.
So for anyone asking which approach delivers better results - fully automated, AI-assisted personalisation, or completely manual - I'd say the hybrid model wins every time. Automate the grunt work, don't automate the relationship bit. What setup have you found works best?