Both of falling into the same usual cricketing pattern. Whatever you average in domestic, is likely to be close to what you average in internationals. There are those who do great in domestic, and poor in internationals. Very, very few average substantially more in internationals than domestic. Pandya shows flashes of brilliance but is inconsistent, just how he must be in domestic given his averages.
Same with Fahim, people went on about his talent and how his numbers didn't justify him in domestic. And yet he's produced numbers similar to that in internationals. Fahim is even worse I don't think he's even used to responsibility with the bat, he's batting like a bowler who slogs down the order. Which makes sense, he's a bowler first that's what he knows best.
Both are talented, but both probably picked too early and not allowed enough time to dominate in domestic, and develop the mindset and the ability to regularly contribute with the bat and perform under pressure.
Another argument for Pandya over Ashraf is he's a luxury India can afford. They have a strong batting line up. A hitter down the order who can score quick who can bowl a bit can be of use. Especially given India don't have the plethora of part time bowling options they used to. He's not the clutch finisher down the order that India would love though, once Kohli gets out things get difficult. Dhoni used to fill that role but not anymore.
On the other hand Fahim plays in a weak batting line up where we can hardly afford to weaken anymore. We have quite a few part timers in Malik, Haris, Hafeez who have all been able to bowl 10 overs at times, even Fakhar can bowl a bit. We also have a batting allrounder in Talat knocking down the door in domestic too.
Internationals isn't the place to practice, or worse in Fahim's case learn, that's what domestic is for. If we play him, play him as third pacer and see if he can hold his own. If he can't, think the best option is to send him back to domestic to work on his game.