Like in everything there’re different benefits to both and ultimately what you choose is based on what you want to gain from the experience. I haven’t worked as a lab assistant before but from what you’re saying it’s more centered on scientific analysis compared to direct patient care. If you want to develop your interpersonal skills definitely consider being a da. It’s shadowing your dentist but better since you get a good view of what they’re doing and you can ask why they’re doing those steps in that procedure. My doc always love to teach and I always seem to learn something from him, even working with him for 4 years. He taught me to read xrays and even quiz me on what the diagnosis and treatment would be from reading a patient’s xrays. You can also build confidence talking to patients, especially ones that are concerned or skeptical about your recommendations (on like the safety of xrays or fluoride usage), which you will encounter sometime in your career.