This past Saturday, we went to Hershey Park. It's the first time I've been there over the summer, to ride the rides; (we've been there to see the Christmas Lights before). My bottom line is that with one big exception, I'd rather go to Knoebel's.
That one big exception is the Lightning Racer roller-coaster. It was tucked at the back of the park, was the best ride we went on all day, and had the shortest wait of any ride. Our first time on it probably took us 5 minutes in line, the second time, maybe 10. Simply amazing ride; loads of fun. Son and Daughter (9 and 5, respectively) both loved it. I'd rate it at least a tie with The Phoenix at Knoebel's: not as much airtime, but more unpredictable twists and turns. And nowhere near as rough a ride as on Knoebel's Twister. I'm glad they don't charge by the ride, or I'd be stopping there on my way home from work to ride it, often.
One other high point of the day was the train ride. Hershey's train had trackside animatronics that were fun for the kids, and it was quite a bit bigger, and hence more comfortable a ride. OTOH, Knoebel's longer train ride is much more scenic, going out into the woods like it does. But Hershey's was quite a nice ride just the same.
Now the downsides, at least as compared to Knoebel's. Not as much shade. Way longer lines (except as already mentioned). Much more expensive food, and they check bags on the way in, to make sure you don't bring your own. Way more crowded. More expensive to get in. Paid parking.
I won't belabor the above, except to say that food was more than twice as expensive, and of course Knoebel's doesn't charge to get in, for those adults who won't be riding rides. Wife only rode one ride on Saturday, and it would have cost $40+ for her just the same. (We got our tickets for close to free from Wife's Mom, as Mom-in-Law's work had their company picnic there. Thanks, Mom-in-Law!)
Comparing rides, both places have clean, safe rides. The flume rides are about the same. Hershey's version of the Skloosh is taller. Hershey's has more coasters, and has metal coasters (with plenty of loops). Knoebel's has more for little kids.
Adding it all up, Hershey's vs Knoebel's is $130 vs maybe $60, not counting food, and we rode many more rides at Knoebel's. I loved Knoebel's before, but I'm a bigger fan now.