These are no free breakfasts, everything has pros and cons.
Aegis has very powerful radar which can detect even small RCS targets at huge ranges and with high rate of update, but as result it is very heavy and located low, reducing the detection range of skimmering missiles. Its illumination radars are also very powerful and long range (can fire at 240 km), but they can only address 3 targets simultaneously (to sides, front - only 1).
Sachsen class destroyer has much higher located multifunctional AESA radar (APAR). It can detect skimmering missiles at longer range than Aegis and engage much more targets simultaneously. But its much smaller and as result max range is limited to 150 km (for low RCS even lower). It has also SMART-L radar for long range detection, but this radar has low update rate and it cant illuminate targets and make terminal guidance. The update rate especially important vs ballistic missiles.
Conclusion: Aegis is much better vs. ballistic targets and long range high flying targets. Sachsen is much better vs. big number of low flying targets.