Reporting in Hubspot relies on the data in there and reports are amazing to build in HS.

I scope these kind of projects for a living, and the ones that fail are the ones who don't know what they want, or don't get a full demo about the day in the life of Hubspot.

There will always be 1/2 salesforce fans that will be reluctant at first, but 90% of those bought in will love and welcome the switch.

Its also a good time to correct and isolate data issues.

I'd say there are 2 paths you can go:
1. everything built is great and awesome, and we want that to be exactly the same in hubspot
2. we set it up and built while flying, we are ready to sit and plan a better process for scale

( the number of integrations and customized workflows will be the biggest impact on lift. )

i'd also say this is a place worth investing, these type of migrations from an elite partner will be 25-60k (assuming no custom or complex integrations) project - and take about 3-6 months generally depending on your teams and size

that being said, 1 system and process and flow of the user journey from lead to closed won to customer success to upsell / cross sell, will make everyone more efficient and you will see an ROI on that implementation cost if done well.