IsaSUSY is solving numerically the set of beta functions (2-loop for the gauge, and 1-loop for the other), including thresholds (sharp theta function), using 4th order Runge-Kutta algorithm with fixed step (no accuracy control). Unification is realised numerically with an accuracy of 5 permille.
SuSpect. The french SUSY-GDR (Groupement De Recherche) tools group decided to build their own tool to solve the discrepancies between Spythia and IsaSUSY. This code is solving numerically the set of beta functions (2-loop for the gauge, and 1-loop for the other), including thresholds (smoothed theta function, in spite of the minimal substraction scheme), using 4th order Runge-Kutta algorithm with step doubling for controlling accuracy. Unification is approximately realised with semi-analytical formula (1-loop, no threshold).
MUSE.(tools group).This code is solving numerically the set of beta functions (up to 3-loop for the gauge, 2-loop for the Yukawa and some of the soft breaking terms), including thresholds (sharp theta function), using Predictor-Corrector algorithm with very high accuracy (10^-13 relative uncertainty). Unification is exactly realised through simultaneous numerical solution of the set of constraints. Accuracy of the solution is explicitely provided in the end of the run.
MUSE is designed for speed and accuracy, to be extensible to new radiative corrections, to be used as automatically as possible for scans, and as flexibly as possible when trying to compare to other evaluators. Different level of complexity can be selected through switches.