Snowplow CEO here. We haven't used Jitsu before but are very familiar with Segment. It looks like Jitsu sits in the Segment product family, along with Rudderstack: basically a Customer Data Platform bundle of simple JSON event tracking, Fivetran-style transactional/SaaS data ingest, and then relaying of data out to various SaaS endpoints plus cloud DWs.

Snowplow started at the same time as Segment (2012) but has evolved along a separate tech tree. Micro-service architecture, cloud native, using Kinesis or Cloud Pub-Sub as the data transit, enrichment framework plus a Confluent-style schema registry supporting very rich and versioned JSON Schema-based event payloads. We are built by and for data platform teams; our open-source behavioral data engine doesn't have a UI (our commercial Behavioral Data Platform does). Hosted trial here https://try.snowplowanalytics.com/

Definitely room for both product families in the market! I'm sure Jitsu will do great.