Several years ago I was out in California and played a round at the old Alastair MacKenzie designed Pasatiempo GC.
In the clubhouse display was a set of Juli Inkster used to win one of her Major Championships with.
As shown in the picture I took, the irons were covered in lead tape.
Most people have been misinformed that lighter means better.
Sure you can swing a lighter club faster but normally that also means to the detriment of your control
The golf swing requires a lot of torque in the feet and legs to swing on a proper path and more sequenced motion. If you can wear spikes- at least while practicing- your game will be better for it. 
Lighter doesn't necessarily mean better. You may be able to swing something that is lighter at greater speed- but where in the swing does that speed occur. Remember mass and weight are also a form of distance when the clubhead is delivered properly.
Where the true speed in the golf swing occurs has and always will be debated by golfers & instructors. It obviously make sense that we want the most speed to occur at ball strike.
As many of my followers know, I am an advocate for golf club lie angles that aren't too upright.
Whilst equipment has changed at an alarming rate in the past 20 years there is no substitute for feedback.