Depends on how you define "benefit".

I would argue that Tokugawa Japan's isolationist policy succeeded at ensuring social and political stability and consolidating the regime - and did a great job of it, given that it lasted over two centuries with very little in the way of internal conflict and no foreign war until Perry. (Not that this was the only factor in promoting stability, or even necessarily the primary one, but it was a major contributory factor.) But the enforcement measures were draconian, and despite the trade with the Dutch for western books, technological advancement as a whole undoubtedly suffered relative to more open time periods. And when the policy finally fell - because Japan no longer had the military ability to keep foreigners away - it led both to unequal treaties and the end of the regime.

But again, that end came centuries later, and for a very long time Japanese isolationism meant peace and stability, and I'd think if you were to ask Tokugawa Iemitsu he'd have taken the tradeoffs - it's telling that until the black ships came, no shoguns thought the edicts were a terrible idea and should be repealed outright.

(Apologies if Japan in this period isn't what you meant by "isolation policies" and you had in mind a more total seclusion without trade through Nagasaki, Tsushima, Matsumae or the Ryukyus - or for that matter if you were just thinking isolationist as opposed to interventionist in terms of foreign policy, given that Japanese isolationism went far beyond staying out of war - but it's commonly described by that term.)

This isn't really history, but you'll be hard pressed to find an example favoring protectionism. The general consensus amongst economists is that individual national specialization and subsequent trade is beneficial to consumers, but harmful to the owners of capital of those industries that a country does not have comparative advantage in. The implementation of barriers to trade, such as tariffs and import quotas, creates inefficiencies and loss of value. The mathematical proof can be found in most Macroeconomics textbooks. I'm sure it appears in the standard macroeconomics textbook International Economics by Krugman et al, but I think the best mathematic demonstration can be found in Economics and Policies of an Enlarged Europe by Altomonte and Nava (pp. 34-46 have graphic and numeric examples).

Sudden openness to trade can be harmful for a country that has a small and underdeveloped economy (this was the topic of a recent economist article). The "Infant Industry" argument says that limited barriers to trade can be helpful in the initial phases of economic development, if they are then removed once a country has exhausted catch-up growth. Of course, politicians often forget that last part (again, Economics and Policies of an Enlarged Europe, pp. 46-53).

Historically, although it is difficult to find true examples of free trade, the countries that were the most open to trade were the wealthiest and most powerful, with examples ranging from the Maritime Republics of Italy to the United Kingdom eclipsing Spain and France as the dominant power in Europe.

Thanks for the answers everyone