If the issue's hard work, then that's an indictment on the attitude of our players more than anything else (I could go into the whole "the manager is the motivator" spiel but I won't). Movement for me is also really not an excuse with players like Rooney and RVP; they're smart footballers, so if they're not making smart runs there's an issue with either motivation or tactics. Mata, Kagawa and Januzaj, for me, have shown plenty of propensity to move off the ball and create space.
Pace is the one area where I'd agree there's a difference, but even then it's only Sturridge and Sterling. Suarez moves non stop and is very clever and agile, but I wouldn't say he has blinding pace, and Neither does Coutinho. I also think the quality of those 5 players we can pick from is quite far above the equivalent 4 for Liverpool, with the exception of Suarez who's better than any of ours at the moment. So even if, say, Januzaj or Mata don't have the pace of Sterling they're more than good enough to beat the full back and create danger by running into the box.
The one precise element we wouldn't have is the threat in behind the defence that Sturridge presents thanks to his pace; neither Rooney nor RVP offers it quite so much. But, to be honest, we don't have that at the moment either; Valencia and Young have offered nothing of the sort, even though they're picked to give us some sort of "direct threat". If we want to play on the counterattack, we should just go with Welbeck up top. If we expect to dominate possession and come up against a defensive team, then the threat in behind won't matter, and we should definitely just pick any four of Mata/Januzaj/Kagawa/RVP/Rooney.
Edit: Yes, I should have posted this in the tactics thread..