You wouldn't boil grain, malt, LME or DME.
Do you mean steeping/mashing temps?
Do you mean how vigorous the boil is?
The temp of the boil is always going to be pretty darn close to 212F, depending on altitude. You can make the boil more vigorous, depending on the temp and pressure of the heat source, but once the wort is above 212, it starts to turn into steam, so it really never gets above 212 in the wort itself no matter how hot the heat source is, it just turns the water in your wort into steam faster.
The more vigorous the boil, the better hop utilization is. That's about the only factor in the boil. Consitency is more important than reaching some sort of target temp for the heat source, though (above boiling, of course). As long as you keep it consistent and controlled, then you know your hops utilization is consistent and know your boil-off rate is controlled.
I think most brewers would perfer a nice rolling boil that is very controlled, and not chaotic. To achieve this, the heat source is just a tick above the temp it takes to maintain a minimal boil.
Primary #1 - Midnight Ryeder (Midnight Wheat and Rye)
Primary #2 - Florida Weiss
Primary #3 - EMPTY!
Secondary #1 - Downtown Flanders Brown (brewed August 2012)
Keg #1 - Pina Colada Florida Weiss (smoked Pineapple and Coconut Berliner)
Keg #2 - Cinnamon Raisin Cider
Keg #3 - NONE!
Bottled - NONE!