Diabetes was harder.
I had to stick myself constantly, each and every day, to measure my blood sugar and take my insulin. I estimate that by the last month, I had to puncture myself at least ten times a day (wake up, pre meals, post meals sometimes, just before going to sleep.....and then the shots prior to eating.). I had to give myself little pep talks to do it, and it sucked to squeeze out drops of blood for the test strips. I thought I was keeping that pretty quiet, until I overheard a toddler Habibi saying some of the same things I did, before pretending to stick his thumb.
I also had to keep track of what I was eating more than I did with cancer. The oncologist was just happy that I wasn't wasting away, and that all the stuff I ate was boiled to death or pasteurized so I didn't get some food-borne illness. Never had to count carbs, because no one cared about that. I had to list everything I ate with diabetes in a futile effort to not need insulin at the end (it's very hard to balance a growing baby's needs with your needs to keep the sugars down.)
I felt a little sicker at the end of chemo than I did with diabetes/being a zillion months preggo in the nausea department, but I had more options for dealing with that. After all, I wasn't worried if what I took hurt my cancer cells. I was much more cautious with the gestating Habibi (naturally.)
Can't speak for all kinds of cancer but the kind I had is basically considered "bad luck". Diabetes? People wonder what YOU did to bring it on. Lots less sympathy for that in my experience. If you have a few extra pounds, or look like you do (I bloated up bad when I was preggo, not in a cute way), well.....hmm......what did you expect, fatty?
And finally......shooting up with insulin a few times a day vs one blood test/one bag of chemo stuff per week? No question, it was easier with the chemo. I had to make sure I got enough insulin in the syringe, find a place to shoot up discreetly if we were in public (because if you are obviously preggo and shooting up, you must be a heroin addict or something), and deal with the sharps/make sure I had everything I needed in the travel kit. Cancer? I just showed up at the appointed time, and the nurses/techs did all that for me, once a week.
Do what the doctors say with cancer, and depending on the type/stage, you have a good chance of cure. Diabetes? Not so much. It's your "friend" for life.
I don't want to experience either diabetes or cancer ever again, but if you put a gun to my head and made me choose one?
I'd dance with the Big C again over Lord Beetus, every time.