Is Reel to Reel better than cassette?

Tape quality is always dependent on the tape speed and the tape width. When you increase either, you can make better recordings.
Most consumer reel to reel enthusiasts use quarter-inch tape which is twice as wide as cassette.
The speed of reel to reel tape recorders being variable, typically starts at twice that of cassette (1 7/8 inches per second, IPS) and can be doubled (3 3/4 ips) or quadrupled. Semipro and Studio professional tape recorders can run at even higher speeds, up to 60 IPS