Each day 20,000 PINK is released through POS and 36,000 PINK is released through FPOS. Participating in FPOS means access to greater daily rewards, but at the expense of accumulated network weight associated with staking 100,000 PINK inputs. This reduction of weight for FPOS participants has the effect of relieving pressure on the POS system, improving opportunities for people not participating in FPOS to stake and potentially making it more profitable per coin to participate in POS over FPOS, depending on how many coins are dedicated competing for FPOS blocks.
Converting coins to target FPOS is trivial as competitors will have far less accumulated age compared to POS participants, meaning that a person can quickly target FPOS and become competitive for blocks under the system. If it becomes more profitable to target POS over FPOS due to heavy competition for FPOS blocks, converting back to targeting POS blocks is non-trivial, as established participants targeting POS blocks will have the advantage of increased input age which significantly increases their competitive advantage over other POS participants that are newly targeting those blocks - individuals retargeting from FPOS to POS will have to wait several weeks before their coins reach potential under the POS system, in which time it may again become more profitable to target FPOS over POS.