The verdict
For a small team, I'd pick Keap. You can start self-serve and it covers the whole path from lead to paid invoice.
I'd pick Marketo Engage only when marketing operations is a real job in your company, you run Salesforce or Dynamics, and you need attribution that sales trusts.
Marketo comes with a sales process, no listed prices and a platform that needs an owner. Without one it becomes an expensive email tool. Keap has the opposite risk: a single plan priced by contact count and an early termination fee on annual contracts, so trial it before you commit for a year. If you want a CRM-led option with marketing built in, look at HubSpot before either.