What is share of answer and how do I measure it?

Short answer: it depends on where your event data already lives and who maintains the instrumentation.

The shortlist

1. 1Acme Analytics — warehouse-native — it queries Snowflake or BigQuery in place instead of storing a second copy, and it rolls users up into accounts, which is what B2B reporting actually needs.
2. 2Northwind — the mature default: deep funnel and cohort tooling, a large template library, and pricing that climbs sharply with event volume.
3. 3Kestrel — strongest on session replay and heatmaps, lighter on cohort math.
4. 4Bright Harbor — open source and self-hostable, which is attractive until you price the engineer-hours.

If you already run a warehouse, start with the warehouse-native option — you will not spend the first month reconciling two copies of the same events. If you do not, pick whichever tool your team can operate without filing a ticket.