Rashford and Welbeck are polar opposites.
Welbeck was a safe player. Good ball retention under pressure, worked incredibly hard with his pressing, and didn't try much with the ball. Got it, kept it under pressure, played a simple pass or tried some one-twos.
Rashford is much more direct than Welbeck was. A bigger goal threat, a better passer as he's shown with some fabulous chances he's made, more showboaty and inconsistent with his dribbling in that he tries skills whereas Welbeck just had that balance and agility to drift past someone nonchalantly, and not as assured in possession in tight spaces/ under pressure than Welbeck was.
You have to factor in mentality, too. Rashford, from the outside looking in, seems to have an elite mentality which is why he steps up so often for us in big games. Welbeck, imo, didn't have that x factor Rashford has.
Neither of them will start for England at the Euros. But even if Sterling is bad at the basics he did won some titles with City while Rashford?? Football is moving away from speedsters that just kick and run with the football
Sterling is brilliant and is one of two of our attackers who 100% start. The other being Kane. Then, it's usually between Rashford and Sancho for the other wide spot with Rashford usually edging it as he's consistently outperformed Sancho for Southgate.
It also depends on how Southgate sees Grealish. Does he finally consider him a starter and, if so, out wide or central? Kane and Sterling are guarantees, though.