I'd say it's pretty close. In terms of results I would go with Federer, but I think in terms of sheer dominance Sampras had the slight edge simply because Fed had so many bad losses on HC that year. Either way it's close, but on grass Sampras was CLEARLY better that year.
It's true that Fed did have those bad losses to Canas in IW and Miami but other than that he lost to an on fire Novak in Montreal and Nalbo playing the tennis of his life in Madrid and Paris,not bad losses IMO.
What hurts Sampras is USO,4th round loss against the title for Fed doesn't stand well,If I remember well Pete was coming off from an injury but results are results.
Also Fed was really playing amazing in AO that year,some of the best HC tennis of his life and it will almost definitely remain the only slam he ever won without losing a set.Sampras didn't win AO that year in such dominant fashion,not even close.
Thier Masters Cup performances were similar,one RR loss and dominant display afterwards.
I still pick 2007 Fed on HC mostly because he was more dominant in HC slam that year than Pete in 1994 but it's debatable,I consider 1994 to have been Pete's best year gamewise(for Fed I think it's 2005).