Yes. Using the feat for its utility purpose far surpasses Shield Mastery.
This is incredibly useful for a melee fighter. You see, the biggest plus to this feat is that as soon as you grapple a target, you have advantage on attack rolls against the creature you are grappling, while simultaneously restricting their movement.
For a fighter your ability to hit the target just increased. For a monk, you're in for a flurry of well placed blows that are virtually guaranteed to land. For a Barbarian you've pretty much guaranteed it's not moving away from you. And if you're a rogue, you are getting your sneak attack every turn because you have a teammate within 5' of your target.
Bottom line: This isn't meant for ranged characters.
Grappling with this feat is meant to lock down a problematic target and keep it from going anywhere. This feat gives you the option of restraining a target for whatever purpose you like. For example: You might want to pin a vampire instead of just reducing it to zero hit points in order to bind it and place it in running water or sunlight. Otherwise you won't defeat it. Alternately, you may need to restrain a mind controlled guard or fellow party member so you can subdue them without lethal intent.
Shield Master is a good feat, but has it's drawbacks as well. For instance, you have to have a shield to use it, and you don't grapple the target but instead knock it prone or shove it 5'.
All in all it comes down to your play style and game objectives. If you're running a campaign where there is no clear black and white lines of good and evil, where your characters need to capture and restrain enemies rather than unleashing the murder hobo within, then pinning is going to come in very useful.
I tend to see Shield Mastery as an offensive feat, and Grappler as a Utility feat. There are very different purposes for both.
A question came up in comments with a statement I believe to be incorrect. I'll address that here, emphasis mine.
Prerequisite: Strength 13 or higher
You've developed the skills necessary to hold your own in close-quarters grappling. You gain the following benefits:
You have advantage on attack rolls against a creature you are grappling.
You can use your action to try to pin a creature grappled by you. To do so, make another grapple check. If you succeed, you and the creature are both restrained until the grapple ends.
The wording here, to me, clearly alters your options available under the attack action. It states that you can use your action to pin a creature grappled by you. As grappling is a special melee attack, it can replace any of your attacks made by attacks and extra attacks. Because of this, the second part means that you can:
1) Grapple a target with your first attack.
2) Pin your grappled target on the second attack.
3) If you had other attacks, you could use them in between number 1 and 2, or before or after, really it's your call.
This does not take two turns, and nowhere in the feat does it say it requires an attack action to exhibit the pin. In fact, it explicitly states that you make another grapple to do this. The first portion of the second benefit clearly exhibits the additional ability your grapple has gained.
So why is this important? For a fighter, the ability to grapple two targets and pin them is invaluable when dealing with things that are immune to prone. Why is this important? Because unlike Shield Mastery, you don't impose disadvantage against all of your ranged characters with restrained. Like a good tank, you've given everybody advantage instead of just melee characters.