Which of these sentences is correct?
A) This is the toughest part to me.
B) This is the hardest part for me.
C) This is the toughest part for me.
D) This is the hardest part to me.
Which of these sentences is correct?
A) This is the toughest part to me.
B) This is the hardest part for me.
C) This is the toughest part for me.
D) This is the hardest part to me.
A & D both have 'issues' (wanting something like the intransitive verb 'seems' a la "This seems the toughest part to me."
In any case, both the to examples have different meanings to the for examples, A & D can imply that the object itself is hard, rather than the action(which is what I think you're trying to communicate)
B & C (the 'for' sentences) both carry the meaning that the verb is difficult (that you will find this particular act more difficult than the rest of a series acts.)
Examples:
A) (Points at section of 'recycled' lumber) This seems the toughest part to me
B) (Just about to shift gear for the first time in front of Examiner) This is the hardest part for me.
C) (Just about to shift gear for the first time in front of Examiner)This is the toughest part for me.
D) (See A)This is the hardest part to me.
I'm not sure D really works in that sense, as the adverb/adjective hard looks odd to me anyway in either sense :S