Is it very difficult for Cubans to move to Argentina, Chile, or Mexico? As troubled as some of those places are, they seem like paradise relative to Cuba.
It was very difficult until recently and remains so. But you're wrong to assume that life for the average person is any better in those countries than it is in Cuba. The UN's Human Development Index has Cuba as the 2nd most developed country in Latin America (behind Chile).
The UN's HDI is as fraudulent as pretending PPP GDP is a good way to judge that someone in western China earning $1,000 / month is as well off as someone in Sweden earning $8,000.
It fails to account for a vast number of things that are critically important.
The notion of scoring high on the human development index while living under an extremely repressive dictatorship is more than enough to completely discredit it. Equivalent to the UN allowing Saudi Arabia on the human rights council.
People that have never experienced any meaningful freedom of speech, press or ideas - can have a high HDI? I think that's inherently impossible. What's the value of an education that occurs in the very narrow box of a dictatorship that doesn't allow for freedom of expression, for competing ideas, etc? I say it's worth very little, and it's a cruel joke to rank Cuba so high.
How can anyone properly score Cuba's healthcare system when it almost entirely lacks transparency?
I'm pretty sure the average Argentinian and Chilean are better off than the average Cuban. At least I haven't heard of many people risking their lives to flee Argentina and Chile.