The first difference between those two arches that people realize when they see them is the number of archway. The Arch of Titus has just one archway but the Arch of Constantine has three, A bigger one in the middle and two smaller ones on the side.
Then is the difference of size. The Arch of Titus is 15.40 meters by 13.50 meters and 4.75 meters wide, The Archway is 8.3 meters by 5.36 meters (www.aviewoncities.com) The size of Arch of Constantine is 26 meters by 21 meters high. (www.aviewoncities.com)
According to the module 5, Page 10 The Arch of Constantine was built in 312-315 CE, It is a triumphal arch to commemorate