My company is in the process of switching to an HSA-type medical insurance plan. My understanding is that an HSA can pay for eligible medical expenses including Vision and Dental. If this is correct, why would I also need a Limited FSA to cover Vision and Dental?

Am I correct that ALL HSA's cover Vision and Dental? My employer also provides Dental Insurance and Vision Insurance...does that impact the ability to reimburse those costs via the HSA?

$ can be withdrawn from an HSA tax-free to pay for health insurance premiums or out-of-pocket medical expenses that meet the definition of IRC section 213(d). So, yes, most vision and dental expenses would qualify.

With a limited FSA you can have more tax free dollars. By using a limited FSA while you have high deductible health plan (HDHP) coverage that makes you eligible to make tax-deductible contributions to the HSA, you end up with more tax-free HSA $ for future health expenses than if you did not have the limited FSA and were taking $ out of the HSA during the same year you are making contributions to the HSA, to pay for Vision and Dental. The limited FSA might be used to pay for deductibles, co-pays, co-insurance regarding the Vision and Dental insurance, and for vision and dental items perhaps not covered by that insurance.