"Xが好きな人" is ambiguous and means both "the person who likes X" and "The person X likes",
but in this contest, it's obviously used in the first sense (see comments below).
Actually, わたしが好きな人 and わたしを好きな人 are the same here. Both noun phrases inside the quotes are about "the person who likes me (who is はっきりとしている or していない)", not "the person I like".
The verb はっきりとする means "to show a clear/definite stance", "to say things clearly".
- ([はっきりとしてくれない]わたし) が好きな人 = the person who likes (私 who doesn't say things clearly).
- ([はっきりとしている]わたし) を好きな人 = the person who likes (私 who says things clearly).
EDIT: As @goldhick and @marasai pointed out in the comment section, this sentence can still make sense if the first noun phrase means "the person I like". I didn't notice such an interpretation is possible.
If the first phrase means "the person who likes me", as described above, the whole sentence essentially means "I'd love a person who loves me because I'm a kind of person who says things clearly".
If the first phrase means "the person I like":
- [はっきりとしてくれない] (わたしが好きな人) = (the person whom I like) [who doesn't show a definite stance toward me]
- [はっきりとしている] (わたしを好きな人) = (the person who likes me) [obviously]
The whole sentence essentially means "I'd choose someone who definitely loves me, rather than loving someone who may not love me." If this is the case, はっきりとしている in the last phrase is used differently from the others.
Choose whichever matches the context.