i've got both HEM2 and PT4 and use hem2 out of preference. They are both owned by the same company though so eventualy the technologies will probably be merged . HEM2 is multi threaded so takes advantage of all the processor cores you have , whereas PT4 is single threaded so just runs on one core. this gives HEM2 a speed advantage importing large numbers of hands . HEM2 also has a better designed database , whereas PT4 has a fixed database design, if they add new features they have to adapt the database and since that is single threaded can take forever with a large database. HEM2 doesn't have that problem but requires a better spec of computer to run The more memory you have the better .