Bottom line is you have to be eating over maintenance cals to grow.
But, there are different schools of thought on this. It also boils down to how you personally respond to the training methods.
I used a typical split (Mark Alvasi's, I think) and used it for about a year and it worked great. I tried Max-OT (4-6 rep range) for about 2 months and got incredibly strong, got some great growth out of it. And I've since returned to more of the traditional ranges 10-12 while I cut.
Just try each for a while (not just a day of this here and there) and see how your body takes to it.
The reason you're more sore after doing 30 reps is just because you're tired; think about it. Different rep ranges all serve their purpose, as far as I'm concerned, but think about it - if you're doing something you can rep out on 30 times, it's really not all that much weight. It's like doing ONLY pushups and expecting a Phil Heath chest. It's like the women you see doing lateral raises with the 5's for sets of 50.
Different muscle groups will respond differently (or better) to certain rep ranges, but I don't think any muscle group needs to be worked at that level (other than maybe calves). You also have to factor in form. You mentioned curls. I read a great article by Chad Shaw (thenaturalone on bb . com) about this. Some people can use significantly less weight and get awesome bis compared to the guy lifting twice as much - but he's swinging his shoulders, not squeezing his biceps at the top of the rep, not pulling with the bi initially, etc.
There are a lot of different factors in play here, so there's not really one good answer other than - try both for equal amounts of time without making changes to any other variables, compare results (which very few people want to or are willing to do).