Don't forget C3 is outlawed on most bike paths, so depending on where you live and ride this may or may not be an issue.
Around here in Orange County, there's a bazillion bike paths that people love to ride, so the C1 bikes are super popular. Now they've classed 1 with 2 so either is okay, C3 is still prohibited for speed, only allowed to ride on roads/street. That said, there isn't much (if any) enforcement so as long as you keep a cool head and are polite no one knows what you're riding, so the C3's are not uncommon. I imagine in a national park or some trail with a ranger things might be different. I just hate being hassled so I would tend to follow the rules so no one is bugging me about it.
For a commuter or someone that rides on the roads C3 makes a lot of sense. Most C2 bikes can be made to go faster if you want it to - devoid warranty or no.
And then there's the question of comfort and safety at that speed - again on the open road it's probly fine for most, but for any kind of congestion or pedestrians on a path it's likely way too fast.
I'm old too...had to give up motorcycle riding for it's injury risk. A C3 bike puts me right back there. Same for offroad, so I've stayed away from the mountain bikes as surely I would land on my head! LOL The drop from seat-height to the tarmac at near 30mph has the potential to be a real killer.
We just finished a geard-hub conversion on her Roll - she rarely ever rides faster than about 15mph. I can tell you the Bafang geared hub is virtually silent, has plenty of pickup and go, you don't even have to pedal if you don't feel like it, and there's no drag if it's unpowered - ZERO.
I also just got the Giant Explore with the Yamaha mid-drive, and it has smoother engagement, similar in power assist, but drags A LOT unpowered. I really would not want to have to ride it home with a dead battery. Uh, no.
We haven't used them enough to compare power consumption - her's is 48v, mine is 36, both are 11-12ah in capacity. My best guess is the Explore will have at least 25% more range, just because of the mid-drive efficiency through your cassette gears - and you're always pedaling with it. If she becomes a 'throttle-rider' she'll use up her battery in short order.
I'm not completely sold on either as being better than the other. I will say that you can buy a pretty nice geared-hub ebike for considerably less than most of the mid-drive options. I have about a grand more in mine compared to hers, and they both do basically the same thing.
So I get it with the C3 fans, but there are other considerations than just finding a higher top speed.