It all depends what your needs are. If you need the points this year take Murphy as he will be on the PP with Bouwmeester in Florida. Murphy had a very strong year in Europe and showed at the Worlds he can play against NHL players.
Russell and Franson are both prospects with huge upside. Russell has dominated the WHL the last couple of years. Franson is suppose to be the real deal with huge offensive abilityies, so if you can wait for him to develop I would say to pick Franson.