Gundam Breaker 4 is a solid game that's quite fun and offers almost limitless customization. If you're a fan of Gunpla and the Gundam Franchise, you'll find this game quite enjoyable.
However, I will say that this game does have some flaws, like missing features that were once available back in Gundam Breaker 3. Like specific enemies showing up in certain missions, Weapon-only skills that you can level up and can be used on any weapon once you mastered them, Maps you can traverse to find and fight enemies as well as progress the mission, and random AI players invading you that dropped parts you haven't unlocked yet. These were neat features back in GB3 that would have been great to see in GB4. Its' a bit of a shame, but besides that, GB4 still seems like a good game.
In GB4, now you can scale and adjust parts, you can even have two different arm parts, you can now carry 2 melee weapons and 2 ranged weapons, you can both unlock and save color palette sets for your Mobile Suits, and the new diorama feature is so good to pose and recreate scenes from the numerous animes.
Plus, this game also has working Multiplayer, so it's great fun to play with friends or even random people. Although I think GB3 still has more better features, gameplay-wise, GB4 is STILL leagues above AND better than New Gundam Breaker, and that's what really matters.