PHost 4 supports up to 999 ships, as do some versions of HOST. Most games still use the old 500-ships limit, though.
Build Queue: PHost implements a Build Queue for which can be operated in three different modes. HOST has a simple round-robin queue with priority builds.
Cloning: In HOST, cloning becomes virtually impossible after the ship limit. In PHost, clone orders are normal ship build orders which walk the build queue like everyone else.
In HOST, there are some restrictions to cloning: you can't clone a ship you are towing, and you can't clone when there's a loaded Firecloud at the base. No such restrictions exist in PHost. Newer HOST versions also relax these restrictions again.
In HOST, you can build and clone at the same time when you have more than 20 PBPs. PHost has an inherent limit of one ship per turn and base.
Build Points: PHost's build point system differs from HOST's PBPs. The PBP queue works similar to HOST's PBPs, but not identical. One major difference is that HOST's build points do not kick in until there are less than 50 slots free, PHost's build points are always available. In return, HOST forces you to do a priority build when you have the most PBPs, PHost does not.
Parts in Storage: The dmp friendly code will not cancel a build order, and will not recycle parts required for the ship build. When a starbase has a pending build order, PHost will not allow Super Refit to use these parts either.
Canceling Build Orders: When you are using a Maketurn program which supports it, PHost allows you to cancel build orders after the ship limit has been reached. All Maketurn programs known to support this feature are listed in this FAQ entry. With HOST, the dmp friendly code is used to cancel build orders and recycle parts in starbase storage.
