We have many interesting upcoming match though:
Manchester United vs Viktoria Plzen, Manchester United.
Roma vs Braga, draw.
Ajax vs Lazio, Lazio.
Rangers vs Tottenham, Rangers.
As bad as Manchester United that we know, it's really impossible to see them losing against weak team like Viktoria Plzen.
I agree with your two choices and disagre with two other choices. I think Manchester United, Roma, Lazio and Tottenham can win their matches. Manchester United and AS Roma are improving with their new coaches, not too much but improvements are there. Lazio is on fire in Serie A and they can bring their good performances to Europa League. Tottenham are better than Rangers in quality and I believe they can have a winning even in a home-away match.
For Roma and Porto I have no doubt that they will be able to win the match easily because the opponents they will face are not that difficult and in terms of strength Roma and Porto are still better, those who play at home of course have much greater motivation to win the match.
Roma and Porto are stronger than their opponents and they have a home stadium advantage in these matches. Roma even are still handling their crisis, in my opinion will be able to get this important win in Europa League. With Porto, I agree that they have better chance to win than Roma because they have better form than Roma.