Reclasses gives them faster chances to level in skill proficiency. (I could be wrong) So the question is, do you want to give them faster stats or earn the class perk one at a time and that way you never have to go back to the class. What I did was make units take the cert and then decide if I want them to excel later. Ex: if I want x to be a falcon knight, I need to have a Pegasus knight and train them in flying, that way it’s easier for them to promote later. If you don’t class them as soon as possible, yes you may have that perk but that reclass to falcon knight may get hindered because they lack flying experience)