There's no good reason to use md5, period. If performance matters and security doesn't, use something like mmhash3. If security matters and speed doesn't, use something like SHA-512 (optionally truncated to 256 bits). If both matter, use something like siphash if a prf will do or blake2 if you need a true, high-speed cryptographic hash.

(Actually, besides portability and interoperability, there's probably no good reason to use SHA-anything over blake2. Although if you are working in environments that provide hardware crypto support (Intel SHA Extensions on Atom, now also supported on Ryzen so maybe we'll see it on the desktop, too), SHA becomes faster than blake2 and you should use that instead.)

If at any point you find yourself in a situation where your hash being computed too fast poses a security risk, that should be a HUGE warning. Hashes should be fast, cryptographic or otherwise. If you need a "slow hash" you are probably looking for a derivation algorithm and not a hash and should be looking at scrypt, bcrypt, or even pbkdf2.