This is a game of semantics here: you said fewer warts, I think Mauigoa doesn't have a lot of warts to his game. I think Love has some too, or warts to his resume as a prospect I should say.
And it doesn't matter about grade..this is silliness. Hypothetically if a FB was grade a 97 and a QB was graded an 89, and you needed both, would you take the FB? No because positional importance matters. And I'll argue that tackle is more important than a RB since a tackle plays every place and influences both the pass game and run game mightily.
Roster construction also matters. The Cardinals don't have one RB, but they do have multiple decent, NFL caliber players. At RT the Cardinals have...Wilkerson, who blows. So if two players are close at positions of need, which Mauigoa and Love are, you take the player you need.
Here are Zierlein's grades over at NFL.com. One quick note, only one player has a "Pro Bowl" grade. YIKES.