There's also a huge difference between people who want to move to a new country to build a new life and contribute to society in their new home, people who want to flee persecution and build a new life somewhere safer (contributing to their new host society), and people who just want to go where they get the most free stuff and live like a leech on the back of everybody else.
Personally I'd opt for a looser immigration policy with a much tighter welfare policy, that effectively says you're welcome to come and live here unless there's a specific reason you're considered undesirable (e.g. a criminal, terrorist etc) but don't expect anybody to be paying for you to live here. If you want to come and live in an expensive city like London, New York, LA etc then have at it, but be aware that the streets are cold at night if you can't afford a place to live.
