You have to try by yourself. Even if 10 people will tell you it feels same it won't guarantee you won't feel difference )
It very depend by personal preferences and your level
Why someone who use T05fx will change to H3? Its very unusual change from soft tensor to hard tacky chinese rubber. If someone using T05FX most likely will change to T05, T05 Hard or Dignics if he wants harder and faster rubber
Why not other way around? Fast blade with slow rubbers then upgrade rubbers on same blade? I think changing blade make even more impact on your game then changing rubbers