This is mostly Sakura's durability vs Natsu's.
Sakura and Natsu aren't that far apart in speed if apart at all, so let's skip that.
If Natsu didn't have Laxus' power then this would be more of an even match, but physically Natsu's stronger and with Laxus' power added onto his he's shown some more impressive feats. Poison would be a problem since Natsu is pretty much equal to her in speed. If Sakura's poison were to hit it wouldn't be very useful since Natsu ate Etherion (another internal attack) and managed to conquer it.
If Natsu didn't have as much stamina as he does, Sakura would have a better chance. However, Sakura healing won't save her from Natsu blitzing her with enough power. Sakura's stamina is no doubt low compared to Natsu, who's taken down strong opponents when injured. (He's had help most of the time, but still a feat with some of his opponents).
Natsu takes this mid-high. Sakura can't last long enough from healing, and her destructive power won't be of much use due to Natsu's durability. If we left this to physical strength alone then it would be a different story.
Nice to see members on NB that doesn't hate natsu .
I thought most who chose him because they hate sakura more (because they dont even know natsu yet choose him)
But i was wrong
Lol I hate Natsu and I love Sakura, but I'm just being factual.