Well, not so...
Serenade is a system & circuit simulator (linear and nonlinear) It lacks of an integrated full wave pasive structure simulator. You can use Ensemble for planar multilayer structures and HFSS for 3D ones.
Microwave Office is a circuit simulator (pasive, linear active and nonlinear active)
If you want system simulator from AWR you can use Accolade (see their web site)
HFSS is a pasive 3D electromagnetic simulator. HFSS is the name for two distinct products, one from Agilent and another one from Ansoft. In the beginings (long time ago) there was only one from HP.
ADS is a system & circuit simulator with an integrated planar multilayer structure simulator (Momentum). If you need 3D analysis, you can use Agilent's HFSS
Aplac is a system & circuit simulator with an integrated pasive structure simulator very different from Agilent's. Momentum and HFSS use MoM and FEM in the frecuency domain but APLAC uses FDTD (Finite Diferences in Time Domain); something like CST Mwave Studio (not really, only true for the Time Domain part :smile
Both, ADS and APLAC, aren't tools easy to use
For an RFIC or System designer they are really usefull but their learning curve is a bit stepped. Perhaps APLAC is less hard disk hungry but behind ADS are EESOF and Berkeley's PTOLEMY simulator engine.
Buff, I hope this helps...