Having dealt with both, there is a difference. Corporate M&A is corporate finance. Their teams come from investment banking backgrounds and are not equipped to evaluate early-stage investments. They therefore don’t get pitched them.
Corporate VCs, on the other hand, exist to evaluate young companies and write small checks. The market know that, and therefore shows them early-stage deal flow. (Whether this be founders pitching directly, competitors mentioning them, or investors or their LPs or lawyers getting chatty.) This flow provides different investment and intelligence opportunities from the corporate finance flow.
Practical example: if you’re pitching corporate M&A, it tends to start with an NDA and a data room full of financial models. If you’re pitching a corporate VC, a one-pager and high-level deal terms can kick directly into negotiations.