What's the difference ? What runs better on old "was a 5/10 speed" and now is a "7/14 speed" freewheel/chainwheel setup ?
Generally, use the fattest chain you can. Seven speeds like 7.3mm chain best. 7.1mm 8-speed is a second choice.
Skinny, modern 9speed chain costs more, wears faster (as noted in the post just before yours from the mysterious Mr RP10128.)
Wear is noticed at the rear but any problems shifting a too-skinny chain are more likely in the front. Older front changers shift a chain with rivets sticking out the side better than our new smooth ones. A too-skinny chain can fall between the chainrings and wedge them apart.
-- Andrew Muzi www.yellowjersey.org Open every day since 1 April, 1971
