Powerrack with two sets of pins, I prefer powerrack isometrics any day. It's just nice to feel the weight move, even a little.
Isometrics
This is an excellent method of increasing strength that is rarely used for a variety of reasons.
Probably the main issue is, as Steve W stated, "...It just didn't feel as satisfying to push against the pins compared to completing a regular rep with a given weight."
The solution is...
Functional Isometrics
1 ) "The Power Rack with Two Sets of Pins": A loaded bar sitting on the bottom pin is driven into the top pin. With each set you increase the amount of bar weight, driving it into the pin.
2) The Power Rack with One Pin and Bands: A loaded bar with bands attached is used. The bands are wrapped so that the resistance is so strong that it elicits the same effect as placing a second pin higher, as in the first example.
That bands slowing the bar and eventually stopping it complete before lockout occurs.
I have a Bungee System that I prefer.
What differentiates the Bands/Bungees from the use of pins, is...
a} No clanging of the bar when you drive it in to the pin.
b) The Bands/Bungees allows you to accelerate a light to moderate load with a lot of /speed/power.
The Bands/Bungees, when attached correctly, slow you down before you reach the Isomectric position.
Slamming the a light to moderate loaded bar into the second pin in the rack is a jarring effect; not the case with the Bands/Bungees.
Benefits of Isometrics
1) Develops Strength 15 degrees above and below of where the Isometric is performed; allowing you to work on a specific weak/sticking point.
2) Maximal Muscle Fiber Recruitment: An all out maximal Isometric ensure all muscle fiber are engaged, increasing strength.
3) Recovery: The quickest recovery occurs with an Isometric Action and a Concentric Contraction.
Kenny Croxdale