For me, it's been a mix of experiences.

I started when I was 8. My Dad took me to see Eric Clapton, and I knew from then I had to play. Thing was, I got given a classical guitar and spent the next 4 years learning classical & flamenco styles through school, playing in the orchestra etc. That was difficult - I remember finding it hard with small hands to do what I needed to do.

I learned a lot, and was fairly good at fingerstyle stuff, but I got frustrated that it wasn't what I wanted it to be - I wanted to play like I heard clapton play, and I couldn't connect it to what I was doing. I stopped playing for a couple of years.

I got an electric guitar for my 15th Birthday and started learning to use a pick... found it far easier and for the 15 years since 95% of my playing is electric. I found it hard to build picking speed, because it was all new, but all the fretting hand stuff was easy because it's second nature. I'm still learning, but the pleasure of it means it never feels difficult. The exception to this is learning a tricky track to teach someone if I don't like the track. I find new things come to me fairly quickly because I'm so familiar with the guitar, but the boundaries are still there to be pushed.

As for comparison, it depends how far you take it. I've been playing most of my life, and will probably play for the rest of it... so it's like persuing the mastery of anything else - more dificult than a degree, driving etc. I don't think you can learn guitar passively like you can academic stuff - you have to want to learn, I guess motivation is the key - nothing is difficult if you want it enough... maybe?