duplicate linked or group

is there a difference in performance between objects duplicate linked (copy via <alt+d) and objects (Ctrl G) and add group.
i prefer duplicate linked because it’s faster than create group then add it
what is the best duplicate linked or group?

linked = object share the same mesh data, change 1 object others change as well. (saving performance)
group = just a group of objects.

if you use many of te same objects, linked is the way to go.
if you have buildings, lets say: out of 10 objects, then create a group and link that group in.

So in short, if you use multiple of the same objects link it.