Carwin is definitely the the most physically strong guy that Lesnar has faced. He won't be able to so easily throw him around like he did his other opponents. But, I still think Lesnar (at least before his medical issue) is the stronger guy. Carwin is the technically superior guy, probably some of the best technical boxing skills in his division. But, what I don't think Carwin has is Lesnar's speed.
* Technical Striking
* Knockout Power
Although, it's anyone's guess how Lesnar will perform now post-illness. It's possible he's lost some of that speed and strength.
Could go either way, but I do think that right now Carwin has the best chance at taking out Lesnar. I do hope Carwin wins. He's a humble, intelligent guy and helps bring a positive image to the sport. Lesnar is and has been doing the opposite, I think.