Spray foam or blown-in?

Start with the attic boundary, not the price per bag or kit.

First, check what the bid insulates

An attic-floor bid and a roofline bid describe different surfaces and different jobs.

Keeping a vented attic?

Seal the ceiling plane, keep the ventilation path open, then add the documented loose-fill product.

Moving insulation to the roof?

Design the slopes, gables, eaves, moisture control and fire protection as one enclosure.

Look at the ducts, too

A roofline can bring HVAC inside the enclosure only when boundary and mechanical details are resolved.

Make the two quotes comparable

Match the boundary, area, thermal target, air sealing, ventilation, HVAC and required protection.

Ask what will be documented

Keep coverage and depth records for loose fill; product, conditions and thickness records for foam.

A practical starting point

For an accessible vented attic, consider ceiling air sealing plus blown-in. A roofline needs its own design.