Depending on your soil type you cant always use a vibrator plow.
Correct , if its rocky and super hard packed clay , trench it . If you can dig in it with a shovel get plow . Bought mine in 1982 , there has been 1 job I couldnt do , there were boulders just under the surface , but then again I couldnt have done the job with a trencher either , It needed a rock saw.
This past summer , a landscaper with a trencher was putting in sprinklers across the street from us where we were installing an irrigation system , similar size lots , we installed 10 zones using a plow in less than 2 days with 2 men , lawn looked perfect when we were done , like nothing ever happened, across the street 6 guys 4 and a half days 7 zones and the lawn looked awful . About 2 weeks later we had a 4 inch rainfall in 1 day and the trenches settled about 2 inches , 3 guys and 4 yards of dirt for them to finish the job . Their customer called me to winterize the system .
If you can use a plow buy it , time is money , it WILL save lots of time and effort.