The paste that comes with most heatsinks is fine and the difference is usually a few degrees at most. If you intend to push a high overclock though it won't hurt.
Artic silver 5 is not a modern paste or a very good choice. Its not awful but its been 10 years since it was a great choice.
www.tomshardware.com/reviews/thermal-paste-performance-benchmark,3616-7.html