Yes, William's is much more fake because the way they filmed and marketed it was "Earthshot set up a burger fan in a public place but when random passersbys stopped, to their surprise William was inside!" When actually it was filmed on a closed off street, the "random passersbys" were all cast ahead of time, they knew William would be inside the van, and were being directed to act completely shocked and surprised to see him (even doing bits direct to camera saying "I was so shocked to see Prince William I froze"), and then directed to act engaged and interested in William's lecture about climate change. It was all scripted and staged.
The news even reported on it as "William shocks diners with unexpected appearance in burger van" so they're clearly trying to pass it off as real.
Not to mention the hypocrisy of William delivering a lecture on environmental issues when his private jet use is so high and he owns his own private helicopter which he routinely uses to travel short distances between his various houses.
Whereas Harry and Meghan didn't make any pretence that the phone calls had been pre-arranged ahead of time and the young people obviously had been told to set up a camera ahead of time and knew to expect a phone call.
When the first girl answers the phone Harry and Meghan literally say two words, don't introduce themselves or give their names, and she immediately says "Oh my God" (not in a surprised way, but the way anyone would if they were introduced to a celeb and couldn't quite believe it) but it's an audio-only call, not a video call, so how would she even know it was Harry and Meghan just from the word "hi"? Obviously she'd been told ahead of time "please arrange to have someone filming you for 2pm and Harry and Meghan will phone you at 2.05pm."