Yes, I've noticed that too, sweeter, crunchier, juicier...so I always buy it with seeds.LOVE watermelon, however it's served. I prefer the ones with seeds; it seems to me they are sweeter.
In San Diego back in the 60's there was a stripper who had huge ads advertising her appearances. Her "stage" name was "watermelon Rose".
I like watermelon pure and simple but when I do fancy, I like chunks with slices of kiwi and a few fresh blueberries.