The experimental technique in COMPASS is well established. Experiments with polarized muon beams and polarized targets have been active at CERN during the last 20 years. On the other hand, the acceleration of polarized beams to high energy (100-250 GeV at RHIC), the accumulation of polarized protons in storage rings at 100 GeV and more, the precise measurement of their polarization and the monitoring of beam polarization fluctuations are far from trivial tasks to be achieved. Encouraging results were obtained with the use of siberian snakes at lower energies, but additional studies and developments are needed before they become a fully operative technique.
The experimental setup proposed in COMPASS is a dedicated apparatus,
capable of several different measurements, based also on a long experience
in this physics sector.
The STAR and PHENIX detectors at RHIC are experiments designed for
heavy ion physics and they need substantial upgrades to meet some of the
requirements for the study of spin effects in polarized proton collisions.
Their small acceptance limits the accessible kinematical region.
In particular the PHENIX acceptance, with a coverage of |y| < 0.7,
appears too small for the prompt- 
plus away-side jet studies.
Both experiments will measure jets with electromagnetic calorimeters
only, which rises problems on the containment of hadronic showers
and precise energy determination.
The high luminosity option is essential to obtain sufficient event yields.