The Moon rises tonight about the time twilight ends. For the next two weeks a portion of the night will be moonless, growing longer each night. Technically Arcturus is 0.08 magnitudes brighter, so don't be surprised if you couldn't tell. What should have been more noticeable is the color contrast between the two stars. One is considered white, the other orange.
Most observers describe Arcturus as yellow or orange.
The Summer Triangle dominates the eastern sky these evenings. What appears as a single 4th-magnitude star becomes two stars in binoculars or to the keen unaided eye, and each of those in turn split in two under a moderate amateur telescope. The Moon is out of the way, so once evening twilight ends the sky will be completely dark a perfect time to enjoy the Milky Way. The hazy pathway that marks the rim of our home galaxy rises out of the south, passes through the Summer Triangle in the east and disappears in the north. Binoculars are the instrument of choice for the Milky Way, although a comfortable lounge chair alone is sufficient.