The last of the Mk5 and 6 Escort RS2000's were not the best driving cars and have less bhp and torque than the current Fiesta ST.
The RS Turbo versions had less power and didn't like corners too well. Even the RS Turbo and RS1800 Fiesta's were great in a straight line but you didn't want to push them too hard as they didn't like it. In addition to this, the Fiesta RS1800 has roughly the same bhp as the Turbo (132bhp) but less torque.
I love the driver feedback and grip this new ST gives compared to previous models and is a much better driver's car. The problem with the last of the RS's is that the style and image was dumbed down and never had the same effect or presence as the firs MK1 and 2 models, which were fab and more powerful.
The RS name has only started getting notoriety again due to the Focus RS, which is why they released them in small numbers.
The new Focus ST has performance, power and chassis grip equivalent to the Escort Cosworth and more rewarding than the Sierra Cosworths.
Also, you don't have the electric problems in the new Fiesta that the old Turbo's were plagued with.
Chris