None of the two, really. But if you put a gun to my head and asked me to choose between Weghorst and (this version of) Ronaldo, i would probably agree with ETH and go with the Dutchman.
One of the main reasons that allow us to deploy a high line and be adventurous with our attacking positioning on the pitch is our intention to press from the front with man markings all over the pitch. In these tactics, Ronaldo is more of a liability than De Gea is in the first phase of our build-up. While it's true that Casemiro is a brilliant footballer, and probably the best in the class at screening the defence, he operates within the frame of a tactical system whose strengths and weaknesses he can fully understand and anticipate. We've witnessed several times what happens when our head's not in, how vulnerable we become and how the floodgates open. You could argue that Ronaldo is a player around whom the tactical plan should be adjusted. But that would have led to a whole season of zero tactical progress, and for what? We would still be miles off City and Arsenal.
We do struggle to score goals, and Weghorst isn't helping at all in that area. That much is true. But do we really miss Ronaldo's contributions? People often look at the positions on the pitch and at the roles. What was Ronaldo's role last season? He was the main outlet around whom the attacking plays were devised, the player everybody was looking for to pass the ball. This season, that player is Rashford. And he's doing fine, more so within the context of how ETH wants his team to play. The problem is that Martial (who wouldn't have been the first option to lead the line, if Ronaldo had still been here) has been injured for most of the season and that Sancho/Antony are still adjusting. But these two are also players who like to link up with others instead of trying to find the forward in the far post.
Weghorst has failed to be a quality option for us, but you can still see the thinking behind his loan move. He's a poor footballer, but he was not the wrong profile for the tactics. And if you think that Rashford would still be having the season he currently does with Ronaldo playing upfront and the manager trying to accommodate him, you're out of your minds.
You can point to the fact that WW is also a terrible target man, and this is probably an area where the manager's expectations fell wide off the mark. A physical presence that would function as an alternative option for us when we decide to go down route one and hoof the ball (which we often do with David). He's incapable of doing that. But so is the 38-yo version of Ronaldo.
