Depends how you look at it - for £100 million you get a pair that will dominate the P.L for 10 years - with Fabregas and Schweinsteiger you get players that might dominate for 2-3 years.
Look at it this way - De Gea, Jones, Rafael, Shaw, Pogba, Barkley, Welbeck, Januzaj, Wilson - all 24 years or younger - now that could easily be the start of a team that´could dominate the P.L for 10 years.
I can see few better ways to spend £120 million than Shaw, Pogba and Barkley. Schweinsteiger and Fabregas fine - but they will last 3-5 years at best.