I have run a steel phase for 3 years : I think it is like most things in detectoring: it is not some major leap forward with your set up but simply maybe a 5% advantage , but these little steps do add up . I run a 7000 but have met professional guys running 4500 who wont run them out of fear...
Thought I might jump in finally, full time prospector for last 5 years ! I know this will sound like a wank but I pretty much specialise finding the gold every one misses , usually big and deep,