If you do not want to setup lots of expensive equipment and maybe also want to use the system worldwide, then very few would be able to beat Phoenix flt plnng used via SITA/ARINC/Shares res system. I Believe they also have an internet version online or in the pipeline.
ctc LGWCSCO for further details.
Unfortunatly we were recently forced to give it up by our new owners. We have never regretted anything more than that.
The maths involved beat all the others that we have tested.