A hotter pan will bring the surface up to temperature faster (i'm not sure if we have disagreements on this?...) which means the steaks will brown faster, which means less time for the heat to "cook" the sub surface.
Problem is the steak isn't perfectly flat so a higher temp pan won't necessarily brown the areas not directly touching the pan any faster, meanwhile the areas in direct contact will start to burn. The chef taking a look at the colouring will see patches of deep brown near black and other patches still grey so he decides to pan it a bit more. Thus causing a huge sub surface overcooked area.
Keeping the pan at 170C together with lots of butter allows the whole surface to be nicely browned without any bits being burnt. This is fabulous.
The disadvantage is the longer browning time which if the steak is lean will create a overcooked zone.
So, if steak is well marbled, pan at 170C to allow uniform deep browning while the fat content will prevent the sub surface from getting too cooked.
If steak is not well marbled, choose whether you want more browning (use 170C pan method) or for more "rare-ability" sear at high heat until just before any part begins to burn, some parts might be only slightly grey because it wasn't in direct contact with the pan but you have to remove it from the intense heat of the pan into a gentle heat of a slow oven to evenly cook the meat through....
Edited by Sher.eats, 11 November 2008 - 01:05 PM.