I'd pay good money to play an official Touhou game where these to meet. Although think it's safe to the previous miko wouldn't like the current state of the shrine.

Sendai Miko wouldn't get along too well in post-Spellcard Rules Gensoukyou. She's too brutal in a fight.

Maybe the old Hakurei Miko is more brutal, but Reimu is incredibly cunning, especially if given the time to prepare for a fight. Just look how she developed her ability to fly

It's all but outright stated that Reimu learning to fly was due to her own talent, rather than a skill she spent time developing. Lazy Miko.

that's what I mean. She can fly on the sky, that's her innate skill

She "flies" away from reality, ignoring all the rules ever created to go beyond creation and become untouchable, from where she can blast you to pieces if she felt like it. In fact she would unbeatable. No amount of brute force would be enough to take her down

To be honest, I prefer to think that there is a way to beat Reimu's ability to become invincible. Complete invulnerability would make Reimu unoriginal and boring.

imho these two would go along totally fine, true every one got their own way when it comes to a battle, but that does not mean they could not enjoy some peacefull cups of tea while there is no incident, right?
I think both really care for the people, every one in her own way
both use different styles in combat, still both are effective and thats what matters, right?
lastly, the old miku wouldn't allow reimu to be the new one if she wouldn't think for reimu to be fitting, would she?
think about it

Sachiko said:
To be honest, I prefer to think that there is a way to beat Reimu's ability to become invincible. Complete invulnerability would make Reimu unoriginal and boring.

That's really why the spellcard system exists in Gensoukyou: equalizing the playing field between individuals with broken-ass powers and those whose powers are relatively weaker.

Since Reimu can't be hit during Fantasy Heaven, that spellcard has a relatively short time duration. Surviving it without being hit means you beat it, so it's fair.