I think the fundamental factor is whatr purpose of your next appointment with USCIS. If it is to provide more evidence, then a lawyer is not that useful, If the purpose is to persuade USCIS you are eligigble when they have doubt, a lawyer is helpful.
It is all up to the applicant to make a decision after considering benefit, risk, and cost
It is all up to the applicant to make a decision after considering benefit, risk, and cost