since others broke the ice, the low cost highest performance is WinSim. I've used it on a new design for mini LNG plant with 3 turo expanders and power requirements near world class units.
I've just performed an analysis of multiphase flow for 500 wells into a central system making low RVP crude, and multiple LPG products. I also modeled downhole equailibrium of the crude and gas.
I always add, its not the program its the programmer!!! All sims use the same EOS, Enthalpy, entropy data bases. WinSim has the lagest library of data bases and you can import your own if you don't like the 100 published ones.