HubSpot is the better default for SMB and mid-market — clean UI, opinionated workflows, marketing tools that actually work alongside the CRM. The pricing curve gets steep at scale (the Pro and Enterprise tiers add up fast), but you'll know when you've outgrown it.
Salesforce is the answer when "we have specific custom workflows" stops being a nice-to-have. Object model is more flexible, the AppExchange is bigger, the consulting ecosystem around it dwarfs HubSpot's. The cost is more onboarding time, more admin overhead, and a higher per-seat price.