Basically it boils down to there being three diferent things. Powers of the body, mind and soul. Data's mechanical powers are powers of the body, meaning thwy should stay behind when his mind leaves. Solomon's spells are powers of the mind, meaning they go with her mind, but her Highborn Mana is a power of the soul, so it's kinda iffy where it'll go. In Solomon's case, it stays with her body (or should, in my opinion)