For a fixed power scope .. no real difference. In a variable the first focal plane reticle will get larger as you increase the power. In a second focal plane reticle (typical of most American scopes) the reticle stays the same size as you increase power.
One claim for first focal plane scopes is that increasing/decreasing power will not change the POI.... whereas the rear focal plane reticle (because of the nature of the design) "may" change POI as power is changed. ... the other advantage/ disadvantage is that some do not like the reticle increasing in size as it can obscure the target... there are designs that allow the use of the enlarged reticle for rangefinding...but you might want to do a web search for how this works