You sir, don't know what you are talking about. No "agency" will utilise computers with consumer hardware for anything professional. Comparing a computer with mobile GPU, and low voltage Intel Core i7 with a Mac Pro running dual Intel Xeon, ECC memory and workstation graphics card is just plain stupid.
This compares to the iMac, and not the Mac Pro.
I can only speak from personal experience, but the large film studio I work at in LA does plenty of feature and television work and I have seen literally hundreds of 27" Imacs in three of our studio facilities. Most setups are a 27" Imac with a 21" Cintiq, and some of us working with color (like me) also have a color calibrated third monitor. The last three studios I have worked at have almost exclusively used 27" Imacs with an additional Cintiqs for creatives. It has been that way since around 2011.
I can count on one hand the number of Mac Pros I've seen here....