depends on the method of reunification.
suppose the ROC, perhaps under some nut job DPP leader, by some miracle manages to declare independence(unlikely in the extreme) or start advance work on nuclear weapons, then there is little to gain and much to lose when the PRC reunites the island by force.
however if taiwan were to get hongkong type reunification, perhaps even more handoff approach than hongkong, then it has much to gain indeed. first of all it will no longer need to invest in the military since the PRC will provide defence as oppose to be defended against, given that the PRC is one of ROC current biggest threats, well that threat would be gone, and given the PRC is a thermonuclear power, taiwan is safe from all except WW3(not that it has many enemies). financially, it would retain its own currency like hongkong and in fact it would promote economic growth given the inevitable incoming investments from the mainland, much like how hongkong was able to avoid any major crashes all these years including the asian financial crisis and the more recent 2008 recession due to mainland government support, and in fact like hongkong, it would probably pay nothing to the national treasury while obtaining its benefits, also the unpopular conscription system would be gone as well. as for territorial disputes, ask yourself who is in a better position to compete with the japanese and various SCS claimants. as for quality of life, in terms of personal freedoms that it has currently, well that would be untouched. local laws would not be impacted so long as it does not adversely impact national laws.
you must understand that aside from history and maybe sentimental value. PRC interest in taiwan is all about geopolitics. the PRC has no interest in subjugating the people of taiwan, it has no interest in babysitting the people there so long as they are not trying to form an arm group or anything. it has no interest in what limited material resources the island has. even the financial benefit and technological benefit is but secondary.
its primary interest is to remove a military threat and gain a valuable doorway to the wider pacific. if taiwan is taken back, the PLA has its opening to the western pacific, this opens a whole ton of other doors, it would no longer be bottled in the first island chain(without building/renting expensive bases elsewhere, even if that was politically viable in the short term). from taiwan PLA would gain a solid footing for power projection all the way to hawaii. this of course would be terrible news for japan/US since from taiwan the PLA could contest disputed island with japan far easily than from the mainland(from more sides too) and US attempts at "pivot" or containment would be in tatters. in the SCS china would now have a massive amount of resources freed that was previously facing taiwan.