One AC guy says warm the house up when I'm not home, the other says keep the same temp all the time. Who is right?

Short story:

My thermostats are usually set to be 79f from 8-5 when I'm not home and 75f when I'm home.

My upstairs unit is taking 9 hours when it's hot out to cool down four degrees.

My usual AC guy says I'm wasting energy because I'm letting the house warm up and then cooling it back down. His opinion is that if I keep the house at 76 at all times I will see a decrease in energy usage. He made some pretty compelling arguments.

Another AC guy says I want to have the unit off as much as possible and leaving it warm when I'm not home is the cheaper way to go.

I am inclined to go with the same temp at all times theory because it makes sense that maintaining a temp is less work than trying to reduce temp.

Can anyone clear this up for me?

submitted by /u/vicelordjohn
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