Rahane is a class above Shehzad when it comes to caliber and ability. Watch them both at their best and the difference is obvious. Rahane has better technique, footwork is excellent and is against both pace and spin. Shehzad is decent against pace but poor against spin.
Both are poor at strike rotation with Rahane a little better. However, talent is one thing and application is another. Rahane seems to rest too much on his natural ability while for all his problems and shortcomings, Shehzad is the only young batsman in the team along with Shafiq (young in terms of exposure and experience) to have a certain degree of application and intelligence, however, none of our young batsmen come close to the best young batsmen in the world - the likes of Kohli, Pujara, Root, Rahane, Williamson, Smith and de Kock.
Umar, Maqsood, Shehzad, Amin are simply not of that caliber. Jury is out on Shafiq and Haris, I'm interested to see how Shafiq performs at 3 after an extended run in both Tests and ODIs. He's technically a level above every batsman in the country but needs to find his range now while Haris isn't tested yet but the odds are against him because he's a Pakistani and we are not renowned for quality batsman. Whatever the reason - poor coaching, lack of application, guidance etc etc.
Difficult to put Fawad into any category because he's an insult to the art of batting.