Create the tone with the flanger and then compare it to the phaser. The flanger was the forerunner to the phaser. The guitar effect of the phaser gives a more ghostly sound than the flanger does.
Know that you have a lot of choices when you buy a phaser. Analogue phasers don't have as many stages or all-pass filters and the digital. You can get as few as 4 but the number of filters can go quite a bit higher depending on what you buy.
Add a stereo phaser that uses 2 identical phasers for another unique guitar effect. The phaser out-put is out of phase a quarter-wave between the 2 channels of the oscillators.
Go crazy with the motion sensitive phasers. The motion sensitivity allows this guitar effect of the phaser to be controlled by the body movements and hand movements of the guitarist. You can set a sensitivity control to change the parameter of the range of movement.
Create peaks and troughs in the signal when you step on the phase pedal. Link several together and get a multitude of sounds. You don't have to disconnect each time you want to change, just activate them when you want to use them. Try out a few phasers before you select one that you like.