I suspect that in the long run the second mantra will cause more destruction and misery. A country can survive a socialist economy while retaining some of its culture and identity, albeit in bad shape. A western nation cannot survive being inundated with Third World savages.
You make a good point. And the damage down by socialism can be reversed. We are seeing that now in the former European Soviet Bloc countries.
But the damage down by radical Islam will be, I fear, much harder to reverse. The “diversity is strength” folks say don’t worry, over time the Islamists will integrate into their new countries.
Those folks are dead wrong. Many studies have shown that when it comes to Muslim immigrants, the children are even more radical than their parents. Here’s one disturbing study, out of the UK:
http://www.telegraph.co.uk/news/uknews/1540895/Young-British-Muslims-getting-more-radical.html