If same size.... ..Soft gels are easier, but sometimes you need a bigger softgel than a pill for the same dose of medication.
Practice. Pills and soft gels come on different sizes. You can practice swallowing with things like bakers m&m's that may be a bit less intimidating to a child. Just dont overdo the chocolate!
Soft gels. Soft gels are usually easier to swallow and to learn to swallow.