I have not been to Hershey (but my sister has) and she loves it with her girls.
We went to Sesame Place when DS was 3 and I will never go back. It was insanely hot and crowded (it was August, so some of that is to be expected). There were a lot of things that DS was unable to do -- either because of restrictions, or just because he wasn't big enough/strong enough to do them (hard for him to climb a net while a lot of bigger kids are scrambling up it, too.) I mistakenly thought that more would be geared toward toddlers/preschoolers... but I think a lot is geared toward elementary age kids.
In addition, many of the queues were out in the sun and many of the attractions my son was able to do were playground-type attractions. They were limiting the number of people in the attraction at a time so it wouldn't get too crowded (that's good!). But it was a "when someone comes out, the next person can go in" system... and no one was coming out. Sometimes the line didn't move *at all* for 10-15 minutes. Then one family would go in, and the rest of us would wait till the next person left. We waited well over an hour for many things. That's a lot for a little one, especially when you're just standing in the sun.
I've got a whole list of other complaints that mainly stem from it being an older park without planning for the amount of guests it receives (lack of stroller parking, very few water fountains, etc)... but it was not an enjoyable experience. My son who loves Disney, the zoo, the science museum, the playground, etc... asked if we could leave by about 1pm. We went back to the hotel pool and swam.
If I lived close and could get a season pass to do a few things, then leave when it gets crowded and come back a different day, I might feel differently. (That's what we do at our zoo, which is about 5 minutes from our house.) Or if I could go after kids were back in school... maybe. But I will not plan a summer weekend trip there again.