It depend what you need to do.
Both are different. Ps works with pixels and Ai vectors.
I use both but Ps is easiest to learn i think
really depend on what are you trying to do/achieve.
This and end of story!I am into graphic designing, so I can answer your question better:
Adobe Illustrator is vector-based software, meaning you can resize image without losing quality, so if you want to design graphics which require vector file, learn illustrator.
Adobe Photoshop is a Pixel-based software, meaning you can not resize it without compromising on the quality of image, so if you do graphics which requires PNG/JPEG files, learn photoshop.
I hope it helps
Good Luck
This.It depend what you need to do.
Both are different. Ps works with pixels and Ai vectors.