It's a single data point, but a coworker got J&J and said he was wrecked the next day.
My close friend also got J&J and had a 102 fever and all the nastiness that accompanies that for almost an entire 24 hours. Pretty bad, but also pretty typical. So far the worst side effect I've seen was a colleague got facial paralysis for a couple days after the Pfizer vaccine. I had Pfizer and had nothing but minor arm soreness.
I got Moderna. My arm was sore for 48 hours after the first shot. I got the second Wednesday morning. By Wednesday night I was feeling not great and woke up yesterday feeling like I had a bit of a cold. Not bad but not great. A bit achy, headache. After coffee and water and breakfast I felt better, and by the end of the day, 36 hours after my shot, I felt 90%. Today I'm probably 98% good. My arm is still a little sore, and there's a little redness and warmth. It's minor but it's there. A friend said after her second Moderna she felt like she fell down the stairs for 48 hours. All in all better than covid.
My second moderna shot was brutal. I got it at 9 AM and almost exactly 12 hours later I was in bed with chills and a fever, hiding under as many covers as I possibly could sweating profusely and very cold. I decided to try to drink water because I knew I'd be dehydrated and all that did was make my body hate me for introducing cold into it while it's trying to burn the virus inside me and get even worse chills. I rolled over to try to sleep and it was just night-long fever dreams. I woke thinking it was 6:30-6:45, right before my alarm because the night had lasted so long already. It was 2 AM. I was only halfway through. Second half of the night went a bit better. Woke up with a headache. Was fine by noon. Wild ride all around.