Yuuka and Yuugi pretty much hurt the same, cos you're gonna die both way.
However, I'd like to say about Yuuka's power:
First of all, we all know that she has a vast magical power (enough to shoot Dual Spark like nobody's business) and a great physical strength (
http://touhou.wikia.com/wiki/Perfect_Memento:_Yuuka_Kazami). So, how much is her powers?
Physic: kinda vague, since she's not in the fighting games. However, let's assume it's hard enough to scare low to middle level youkai. However, with her vast magic and experience for living long, it's possible for her to acquired a skill called "Magic Enhancing" which's similar to Byakuren. If it's true, Yuuka's raw hits can be compared to Yuugi's or Suika's.
Magic: she shoots strong bullets and the famous Master Spark, said to be several stronger than Marisa, way too strong that ZUN didn't let her use it in PoFV. Now let's talk about " Manipulating flowers". First of all, Yuuka doesn't use magic to create flowers, she makes them grow and evolve naturally. Its arguable that those flowers need seeds or not. If they don't, they Yuuka can make them grow anywhere. And that's where the overpowered ability comes in. There are very dangerous flowers in the world, like Lily-of-the-valley, Foxglove with their poison. We know that every creature in the universe has the outside like skin, shell, scales to protect their vulnerable organs. No matter how strong the creature is, if you can damage their heart, lungs, stomach they'll be defeated, even Dragon or Godzilla. So, what if Yuuka grow a bunch of rose inside you? You see the picture, yeah? The thorns will make every youkai in Gensokyo suffer in great pain, the flowers can also set their roots on the organ and leech any kind of nutrient source of your body. I must say it's kinda Yuuka's style to torture the enemy with the thorns, then like the roses bloom out of their mount as they die. Guaranteed death, cos the only way to save yourself is to dismantle the flowers inside, which requires something to open your body inside out. That also leads to another death. At this point, even Yukari can't face the fatality, since the roots stuck on her organs, gapping all the flowers away can remove them but will take a lot of time/mana and the damage is already be done.
The scary thing is, since it's "natural", killing Yuuka won't help. And it's just one way to use her power. Again with the thorns, Yuuka can warp them all her body to make an armor, she can also enhance them with her magic, nobody would hit that, right? (cos you all read JoJo)
However, flowers are beautiful, and Yuuka seems to be far older to use them to kill enemy unless she has to. Let's hope the ex-youkai-moe will just peacefully pass her days making Gensokyo more beautiful.
Ha ha did you get it? I said "ex" because there is Koga- MY HEART AAAAAAAAAAAAAAAAAAAAAAAAAAAAAA