With speed equal, Marisa is not beam spamming so freely against someone who, besides throwing her own (stronger) lasers...
1. Is pretty much used to dealing with beam spam. Fate, Reinforce/Book of Darkness... All of them know how to beam spam. "I'm filling everything in the sky around us with lasers" level of beam spam, so it's not that far from Danmaku either. Didn't stop Nanoha from either dodging or outright tanking every single hit they threw at her.
2. The enemies beam spamming her, most of the time were either at the same level (like in Nanoha vs Fate) or even stronger than Nanoha(vs Book of darkness) and she still took a ton of hits before either winning or lasting long enough for an ally to come. I don't see how Marisa's danmaku here, having less AP than her durability and barriers, is taking Nanoha out before she herself succumbs to Nanoha's own array os spells.
3. To make matters worse for Marisa, Nanoha can warp and Nanoha can heal. She can use crystal cage which not only seals her opponent but prevents him from using his magic. I won't talk much about her molecular manipulation because it has been a while since I last saw the series.
4. Blaster System. I don't know if she would go so far as to use this in this battle, being friendly and all... But not only she gets a defensive and offensive boost, she can also create bits that can bind the target as well and then launch an attack multiplied in force by as many blaster bits she is using. Whatever she does will be getting a boost of equal force. Meaning if she throws a Divine Buster or an Exelion Buster with 3 BB, all of them will execute the same action. It's like four Nanohas firing the laser together. And the bits are not restricted to one action either. They may bind the target and while the target is dealing with this, Nanoha can already do her thing and be assisted by the bits (like she did in the StrikerS series with Exelion Mode + 3 Blaster + Divine buster).
5. Strike flame: With the same speed and greater AP, if Nanoha uses this, Marisa is not getting out of it unscathed. It's more of a charge sort of attack, a physical blade infused with energy which trespassed even Reinforce's barriers, who was stronger than Nanoha during A's.
6. Marisa's profile doesn't mention magical absorption, but even if she had that, it's not giving her the win in this situation. Reinforce/Book of Darkness had Absorption as well (absorbing the person using magic along with the magic she was using, by the way) and that didn't prevent Nanoha from hitting her with, well, Magic. Also, her barriers give her resistance to magical factors as well, won't be that easy to drain her.
Taking all that into account along with the difference in AP to Dura... Definitely Nanoha. Nanoha has the edge in everything, except speed, and with that equalized.... No way I see Marisa winning.