Which of those boxers will be Anthony Joshua's most challenging / toughest opponents?

[Mr Objecitivity]

I disagree. Wladdy is skilled and powerfully but he's not really full of surprises. He limits his offensive output and the types of punches he throws to protect his chin. And he's not exactly quick. Wilder is much quicker and more athletic. He also throws a lot more punches from angles people who worry about getting knocked out wouldn't throw them from (for better or for worse). I think he has a better chance of catching Joshua with something he doesn't expect especially early in the fight before Joshua gets into a rhythm.

Wladdy is skilled and powerfully but he's not really full of surprises.

Define 'surprises'!

He limits his offensive output

That's because every punch he throws and lands, usually has greater power than multiple punches that other boxers throw and land. It's quality over quantity. Hence, 1 Wladimir Klitschko punch > 3 punches from other boxers.

and the types of punches he throws to protect his chin.

Protecting one's chin is something one should always do if they are a defensively responsible boxer and that's a good thing.

That doesn't mean his punches are any less effective and dangerous because he protects his chin when he throws his punches if that's the point you were trying to make.

And he's not exactly quick. Wilder is much quicker and more athletic.

Wladimir Klitschko is quite possibly one of the fastest super heavyweights of all time at 6 foot 6 inches in height and above 240 pounds in weight. Deontay Wilder may appear faster than Wladimir Klitschko, but it doesn't necessarily mean he is much, if at all faster than even a old Wladimir Klitschko. That's because Wilder throws his punches wildly and widely like an amateur swimmer splashing in the water with all their energy as fast as possible making their movements appear faster than a professional swimmer who's movements appear slower but enables them to cover a longer distance whilst using less energy and whilst making them appear as if they aren't moving as much.

In other words, Wladimir Klitschko moves fast without appearing too fast because he uses less energy and moves with better technique that enables him to cover a specific amount of distance very fast without appearing very fast.

On the other hand, Deontay Wilder moves fast but also appears very fast because he doesn't move with technique that is as good as Wladimir Klitschko's. He covers the same distance as Wladimir Klitschko taking the same amount of time but appears faster because his movements are less efficient.

He also throws a lot more punches from angles people who worry about getting knocked out wouldn't throw them from (for better or for worse).

Which is more of a detriment to him than a benefit because he isn't very defensively responsible when he does so and leaves himself wide open to getting punched by a skillful boxer like Anthony Joshua. He may get away with such punches and moves against inferior level of opposition but not against the absolute best boxers the heavyweight division has to offer.

I think he has a better chance of catching Joshua with something he doesn't expect especially early in the fight before Joshua gets into a rhythm.

I disagree and don't see Wilder having a better chance of landing anything more dangerous than what Wladimir Klitschko was able or incapable of catching Joshua with.

Wilder has taken multiple rounds to stop / KO opponents after he stepped up in competition against better level of opposition who still aren't anywhere near as good as Joshua or Wladimir Klitschko. So the chances of Wilder knocking out Joshua early is lower than the chances Wilder had of knocking out Gerald Washington, Chris Arreola, Bermane Stiverne (First bout) and Eric Molina early. If he couldn't KO them early, then his chances of knocking out Joshua early is even lower because Joshua is a better quality opponent than any of those boxers.

[yankees7448]

Define 'surprises'!

I explained it already later on in my post.

Protecting one's chin is something one should always do if they are a defensively responsible boxer and that's a good thing.

Wasn't suggesting otherwise.

That doesn't mean his punches are any less effective and dangerous because he protects his chin when he throws his punches if that's the point you were trying to make[/QUOTE].
Never said the punches weren't effective.

Which is more of a detriment to him than a benefit because he isn't very defensively responsible when he does so and leaves himself wide open to getting punched by a skillful boxer like Anthony Joshua. He may get away with such punches and moves against inferior level of opposition but not against the absolute best boxers the heavyweight division has to offer.

That remains to be seen. Its a question we can start to answer on March 3rd.