One factor is contribution limits. For a personal IRA, you can contribute up to your compensation from working, with a maximum of $6500 (or $7500 if over age 50). With a self-employed IRA (SEP-IRA), the contribution limit is 25% of your business income up to about $66,000.
https://www.irs.gov/retirement-plans/plan-sponsor/simplified-employee-pension-plan-sep
So if your LLC profit is $5000 per person and that's your only income, a personal IRA will allow you to contribute up to $5000 but an SEP-IRA would be limited to $1250. If your LLC profit was $50,000 per person, a personal IRA would be limited to $6500 or $7500, but an SEP-IRA would allow up to $12,500.
There are other kinds of plans, other rules, and more expert advice is needed. But that is one factor to consider.
