Both riders do the same broad thing. They let you reach the death benefit while you're alive if you can't handle daily activities. Underneath, they're built on different rules.
A long-term care rider falls under the tax code section that governs LTC insurance, 7702B. It usually carries a separate charge, it pays on a defined schedule, often a set percentage of the death benefit per month, and it typically reimburses or pays for qualified care. Because it's LTC insurance, it comes with LTC regulation and LTC underwriting.
A chronic illness rider lives under section 101(g). It's often included at no upfront charge, and it pays through an accelerated death benefit. The catch is that many chronic illness riders discount the payout. You might accelerate $100,000 of death benefit and receive $70,000, with the discount based on your health and life expectancy at claim time. You don't know that number in advance.
The trigger language looks similar for both: usually an inability to perform two of six activities of daily living, or severe cognitive impairment, certified by a licensed health professional. Some chronic illness riders add a permanence requirement, meaning the condition has to be expected to last the rest of your life. LTC riders more often accept a 90-day certification that gets renewed.
Whichever you use, the money comes out of the death benefit. Accelerate $200,000 and your family receives that much less. On a policy also carrying loans, the combination pulls the remaining benefit down faster than people expect.
Pull the rider language on your own policy and find three things: the trigger, whether the payout is discounted, and the monthly or annual maximum. Agents describe these riders in general terms because the general description sounds the same for both. The contract is where they separate.