I find Peronism hard to compute personally. By the time of Peron's ouster he seemed pro-worker, pro-urban poor, anti-capitalist, anti-church and anti-America, positions typically associated more with the left, socialism and communism, yet he has been associated more with Fascism, a movement regarded as more rightist and reactionary. By looking at his friends and enemies in society, Peron seems very leftish compared to say Francisco Franco, and the only thing justifying the association of him with Fascism is his personal relations with Italy.
Peronism was neither Fascist nor Socialist.
For starters, unlike Fascist governments, Peronism was never a full-blown totalitarian dictatorship, but rather a populist authoritarian-leaning democratically-elected government, like modern Chavez in Venezuela... there were free elections and some semblance of free speech, though some newspapers were forcibly shut down and media was increasingly concentrated in government hands, and some opposition leaders were jailed for a period. Peronism was corrosive to democratic institutions, but it was never able to roll over civil society or the Constitution. It was not fully a dictatorship, though (arguably!) it wanted to be.
It was not Socialism either, because it's stated purpose was not the abolition of social classes by the State, instead, in typical corporatist fascist fashion, it saw itself as an arbitrer between the interest of these different social groups. Peronism wanted the State to create a "national industrial burgeoise" through intervention in the economy, tariffs and autarky, while promoting workers' well being through unionization, social welfare and price controls. Of course, in practice, it was a populist government, changing course many times according to the needs of Perón at the time.
Still, if I had to characterize Peronism, it was closer to fascism than to socialism, because of its reactionary origins. Like Fascism, Peronism was a reactionary ideology, born out of the irrational fear of anything resembling socialism prevalent in the Argentine military in the 1940s.
Argentina's Socialist Party had gained some popularity in the 1930s and 1940s, becoming the second party in terms of membership nationwide. (First was the centrist UCR). This, together with Great Depression unrest and UCR Yrigoyen's Second Presidency being a total disaster, led to a distrust in democracy by the Armed Forces, and coups in 1930 and 1943. These coups effectively kept the UCR Party and the Socialist Party out of power, and led to Perón as Minister of Labour, implementing many of the social reforms and welfare policies that would give him popularity among the working classes which until then had supported the Socialists and the UCR, thus presenting himself as the "national" alternative to guarantee stability and direct the workers away from socialism and Marxism.
Using a Marxist term (I'm a Market Liberal, not a Marxist, but I find the term fitting), Peronism fits exactly the definition of a "Bonapartist Regime".
It is ironic, because Argentina's European-style Socialist Party was actually rather moderate, it even supported free trade during the 1930s. It was social democratic, more akin to British Labour than to Republican Spain's PSOE.
In an ironic twist of fate, Perón's statist policies and government control over the economy went much further than anything an Argentina under a Socialist Party limited by proper democratic checks and balances (which the military and Peronism dismantled in OTL), and a fierce Conservative opposition, would have done.