Again people are saying Natsu can't use Dragon Force to try and stop him from winning because they have something against the character etc. The him not willing DF argument is ludicrous, he activated it in Tartarus without ingesting anything as a source of power, therefore it was willed. Furthermore, the restrictions clearly state that the combatants aren't hampered by emotions etc., and they can use anything that they've previously shown, so not counting Natsu's Dragon Force is absurd. By the rules etc. Natsu can use Dragon Force, so thats that.
If I'm going to rate this by stats, here's how I see it falling:
Attack: Natsu >= Jellal
I'd say Natsu in DF or FDKM would match, possibly better Jellal's attack potency when properly serious with the intent to kill (like what Jellal had when vs Neinhart). Its pretty even here but FDKM and DF could put Natsu above Jellal for attack.
Defense: Natsu > Jellal
Its not difficult to see that Natsu has the better defensive feats, previously taking many a beating in battle and still being able to pull through and continuing to fight. Jellal on the other hand hasn't shown a lot when it comes to actually taking attacks. The most recent attack we've seen him take was a small explosion from Neinhart, and he got knocked out by it. Now while I can agree that he wasn't focused on defending at the time, he was still knocked unconscious by it and thats a negative on Jellal's report card.
Stamina: Natsu >> Jellal
Again, it shouldn't be difficult to see that Natsu is the greater individual when it comes to stamina. As per my previous posts, he's been able to continue fighting after taking a beating in a long, drawn-out fight which is better than what Jellal has shown.
Speed: Natsu > Jellal
Now, I'm not denying that Jellal isn't fast, but as we've seen previously when the two fought, Natsu outsped Jellal when using Dragon Force, and thus as he outsped him before Natsu should be able to outspeed him again in Dragon Force. Its as simple as that, as with access to Dragon Force Natsu is faster than Jellal and has previously shown he can catch Jellal with that speed. As Natsu has actually show growth throught out the manga unlike Jellal, it would stand to reason that Natsu in DF now would be even faster.
Intelligence: Jellal >> Natsu
its pretty clear Jellal is the more intelligent one here, even if Natsu has shown to have gotten a bit smarter in recent times. No real debate here.
Versatility: Jellal > Natsu.
Again, I'd say Jellal has more versatility than Natsu here. Not that it would matter that much in this fight, but Jellal does indeed have more versatility with his spells.
I'd say with the better Attack, Defense, Stamina and Speed, Natsu takes this out in the end. Jellal won't be able to stand an onslaught from Dragon Force Natsu (as we've seen previously), and would possibly get taken out by just a few FDKM spells from Natsu. As for Jellal's Sema spell, I'd speculate that Natsu could actually destroy it with a Flame Dragon King's Roar or Flame Dragon King's Demolition Fist. They have the destructive power, and Natsu's previously shown he can destroy things much larger than the Sema spell so he could well render it useless.
I'd honestly say you're kidding yourself if you think Jellal would be able to go toe to toe with Natsu and win anything less than high-diff when Natsu could literally take him out with a few FDK spells in FDKM. Natsu simply outclasses Jellal in Attack, Defense, Stamina and Speed, and in the end that is what will matter, just like their last fight. Natsu > Jellal high diff.