There is no “better” in this situation. Filing a trademark as either an individual or as an unincorporated startup offer the same protections when it comes to your trademark. You need to ask yourself whether you want the trademark to be held by the individual, who could take it when they leave, or by the startup, which would keep it so long as the startup exists.
On another note, why have an unincorporated startup? Incorporate it! Registering your company will provide you with important personal liability protection. In terms of trademark protection, a company that infringes on your trademark has a stronger argument that “it didn’t know about your trademark” if your business is not registered with the state. Register ASAP!
If you want help navigating either the incorporation or trademark processes, head over tofor a free consultations and/or quote from experienced lawyers. Good luck!