No they're not better, but lets be honest- it comes down to this:
Ferrer is the consistent, hard working, 'lives up to his seeding, most times' player. Top seed in Unknown 250? = Wins title, 4th seed in slam?= QF/SF
Berdych, Tsonga, Del Potro - they have extremely good days or bad days. You simply cannot predict how well they will play, yet with Ferrer you can mostly.
Tsonga - Beaten top 3 in every slam, incl 2 x RF wins
Berdych - Wimbledon final, incl 2 x RF wins
Del Potro - US Open win, hurt RF where he dislikes it.
Ferrer - 900000 titles in 250/500, never beaten top 3 in slam.