How many times are we going to have this discussion?
Chrome sockets and extensions are harder, thinner and more brittle, designed for constant torque
Impact sockets and extensions are tougher and more ductile. They act as a stiff spring and can tolerate constant hammering without cracking. If you don't know what mechanical toughness is....
http://en.wikipedia.org/wiki/Toughness
The property that makes the chrome sockets thinner is the opposite for why impact sockets have to be thicker for a given size. It is a tradeoff in material properties.
Using impact sockets on hand drive tools (ratchets, breakers, etc). No real harm is going to be done. Just not the most efficient way to do things, heavy and has been mentioned limited access.
Using chrome sockets on impact tools is just bad all around. It can damage the socket, the impact tool itself and the fastener being removed, not to mention the operator and bystanders. Having said that I know I am guilty of using chrome sockets on an impact. One specific application is for outboard flywheels, where limited clearance is present around the nut and the impact action is needed to brake loose the nut without spinning the engine over. Then again my impact is pretty anemic, so the limited times I have done this my sockets have survived.
I figured that was about it. I need to get a set of Metric sockets for work. I have a 1/2" S/O chrome SAE socket set I got second hand, but no metric. I was just thinking why buy 2 sets of socket (chrome and impact) when I can just buy the impacts and that is all I should ever need. The equipment I work on is never like a car where where socket thickness becomes an issue.
In your case I would probably start with a set of impacts then add chrome as needed. Unless you use a breaker bar a lot, which could damage impact sockets, but not likely unless you really put some force into the breaker bar. Then again you could always reach for the impact wrench if you are using the 1/2" sockets on a stubborn fastener.