That's a tough call. What we've found recently is that as we've adapted our messaging for an enterprise audience, it's resonated less with small businesses. Some companies choose to vary their messaging by audience size (e.g. Shopify) others have one-size-fits-all messaging regardless of size. I think another option is somewhere in between where there are different reasons to believe, proofs and sometimes even value propositions depending on the size of the prospect or customer (but with other aspects of the messaging ladder remaining the same). I think it's difficult for messaging to work for all size audiences though so if the differences are extreme, it's probably wise to force a strategic decision about what audience to focus on before trying to write messaging to work for everyone.
If you can only have one I would defer to the priorities of the business. Are you investing more in enterprise initiatives or SMB? If that prioritization is unclear, I'd use market indicators, opportunity expectations, and recent successes to break the tie.
You can also take a lower-lift approach to addressing the nuance of both. It is likely that your business operates similarly for both targets, provides similiar benefits for your top level business messaging. Then it could be as simple as an additional row of adjusted messaging to target each audience's key pain points and supporting proof points within the same messaging documentation. Then you can cater to the audiences more directly in your activation of the messaging in the market.