bcrypt is also slightly stronger than PBKDF2, since it requires a larger circuit to compute.
The only reason you would want to use PBKDF2 is if (a) you already have a hash and don't want to add blowfish to your code/circuit, or (b) you want to be standards-compliant.
According to the scrypt website, PBKDF2 is weaker as compared to bcrypt and scrypt: "We estimate that on modern (2009) hardware, if 5 seconds are spent computing a derived key, the cost of a hardware brute-force attack against scrypt is roughly 4000 times greater than the cost of a similar attack against bcrypt (to find the same password), and 20000 times greater than a similar attack against PBKDF2."
