Yeah, when I look at Hurst I kinda think to myself he's a bit lumpy looking. But whatever he looks like, he's reasonably effective. I don't think he's a great LT, but he's ok. I think I like him better inside.
And yes, for some schemes a 6'3 340 road grader type guard is great. If you want to run a power gap scheme where these guys need to lever DT's out of position, then you want that. However, when you do more zone stuff, other things become more important like movement, agility and balance. That's not to say a 6'3, 340lbs guard couldn't do that, in the same way a 6'5 310 guard might be great in a power scheme; but generally one body type fits one scheme of the other better.
Ultimately though, it's not about body types, it's about outcomes. Who gets the job done, better, and more often.