OOOOH good fight. I know Namor is hella strong and has the control of waters and what not, not mention he broke out of restraints made to hold the most powerful meta humans [Ult Thor/Hulk?] like nothing, but dont forget that Invincible has been getting stronger [the 400 ton mark] and is tough enough to survive a nuclear explosion in the face like its nothing. Further more he can survive in space, we dont know that Ultimate Namor can do that [doubtful fishboy can]. So even if its just grabbing him then flying into space and watching him suffocate i think Invincible takes this.
I think the main difference was that Ultimate Namor had large-scale hydrokinesis, but his strength and speed were still roughly the same as 616. I don't anticipate the hydrokinesis as being much of an issue. Mark is comfortably faster and stronger, and should be considerably more durable as well.