I think i've seen this thread before. Anyway, deathstrike can cut shred them both into bite-sized pieces and has the best durability and HF. The others can't keep up.
Beast is strong and agile but not enought to avoid being tagged altoghether, she's the more skilled killer and since he lacks adamantium bones she'll likely oneshot him. His HF doesn't seem good enough for this fight either.
Marrow is just outclassed, she has the projectile advantage but LD has excelent reflexes and just waving her hands in front of her should be enough to defend against bone missiles and close in for the kill.