Being a graphic designer and art director for most of my career, I've got years of experience with Adobe Photoshop (but not with a pen). I have to say, I love Photoshop, but not for the purpose of digital sketching. Instead, I love the simplicity of Procreate on my iPad. Sure, it's not as robust like Photoshop, but it has enough to keep your work process streamlined.
Also, for me, it's also hard to see Photoshop as a different tool than what I use for photo manipulation—to actually use brushes for more than retouching, etc.
My only hope is that I get as proficient with all the functionality of Procreate.
I also like that, after paying for the App, Procreate is much cheaper than an Adobe subscription. I don't like that you need to be a subscriber to work in Adobe products. I only wish there was a desktop option of Procreate.
Working on an iPad is another story. I love how portable (like a sketchpad) they are. However, the screen is slick so you don't get that paper-like feel, unless you invest in a really good screen saver. I've got a cheap one that works, but still isn't the same. I've never used a Wacom tablet, so I can't compare. That's the next big investment in my digital art journey.
Back to your question as to investing and learning Adobe programs. The good news about Procreate, is that some of the basic functions of Photoshop are built into the App - mostly layers, color editing, masking and exporting. If you have an iPad (doesn't have to be a Pro), it's a cheap entry into digital illustration, with a much lower learning curve than Photoshop. That makes the transition into Adobe is a bit smoother.