Ethical pros of welfare?

Economically, there are no "pros" to welfare. Quite simply, when you subsidize something you get more of it, and there is no economic advantage to having fewer people working.

For the state conducting welfare I believe there are no ethical pros. When the state (any government) conducts welfare they are forcible taking people's money (via taxation) and giving it to someone that did nothing to earn it. In democratic republics the elected officials use welfare to buy votes (if a politician is giving you money you are more likely to vote to keep them in power) and stay in power.

On an individual I think it would be difficult to claim people have a moral or ethical obligation to look out for the general welfare. For if you say this then where do you stop? Let's say that there is an ethical obligation to feed those that can't feed themselves. Well now you must define "can't feed themselves." This is more difficult than it sounds.

when you are reduced to ethical pro's, you are throwing logic and facts out the window

The leaders are less likely to have their palace stormed and their heads put on the end of a spear, for one