Hi Bill,
A-10A is a Flaming Cliffs module - it has the high fidelity flight model but simplified systems, with NO clickable cockpit. As such it has more limited armament and targeting functionality. However it is still FUN.
A-10C is a full on DCS hardcore, melt your grey matter, take-you-years to fully understand, clickable cockpit and ALL the bombs + a cool targeting pod, module. It's an investment of time and practise, but the payoff is it's more rewarding, flexible to operate and you can undertake a wider range of mission types.
You could the A-10A first to get used to concepts of ground attack flying in the modern air war idiom and then move on to the -C later... but in some regards, the sooner you start on the -C the sooner you get proficient.
Either way happy to give you all the advice and training you need to get ordnance off the rails and into the enemy ground units!