How are PLCs more advantageous than hard-wired Relay?

In general, PLCs are smaller and cheaper compared to the Relays. They are also economically more stable than that of relays and they are very useful commercially. The PLCs are highly reliable and extremely easy to program which is often not the case with hard-wired relays. In simple words, PLCs can sustain in any kind of robust environment even with low maintenance but hard-wired relays are extremely specific in use.