The shared starting point: beneficial ownership
Both schedules arise from federal beneficial-ownership reporting rules. The familiar 5% threshold is important, but crossing it does not tell you which schedule will be filed without looking at the filer's eligibility and intent.
Why Schedule 13D gets more attention
Schedule 13D requires more detail about the reporting person and the purpose of the transaction, including certain plans or proposals involving the issuer. That makes a 13D particularly important when an investor may seek influence or control.
Schedule 13G is a more streamlined path available only when the applicable conditions are satisfied.
Do not convert the form type into a trading signal
A 13D can be strategically important, but the form itself does not guarantee an activist campaign. A 13G can represent a very large position, but the form itself does not prove that the institution just accumulated shares. Read the ownership numbers, reporting persons, amendments, dates, and prior filings together.
Why comparisons should stay holder-specific
When measuring change, the clean comparison is the same reporting holder against that holder's own prior filing for the same security. Combining unrelated holders can obscure who actually increased, reduced, appeared, or exited.