which is better I mean which is more advantageous and is faster and more rewarding
At the Poké Jobs, it takes 24 hours to fully EV train 1 stat(252 EVs). Without a Power Item, it would take 3 Full 24 Hour Cycles. Since the EV training compared to time increases Proportionally, it would take about 2 Days and 1 Hour to get all 510 EVs with a Power Item, and 6 Days 1 Hour without.
The Pokémon Camp only raises Friendship by playing with Pokémon, or raising Friendship, Healing your Poké mon, or boosting their experience by making Curry.
https://www.serebii.net/swordshield/pokemoncamp.shtml#:~:text= Pokémon Camp 1 Playing with Pokémon.,often find other player's Pokémon Camps. More
It's honestly better to just use a Power Item and just Battle Wild Pokémon, but Poke Jobs are faster as they actually give you EV's.
Hope this helps!