There is very little difference in CAT ( capital acquisitions tax) between a farm gifted while alive or inherited on death. The only difference is the small gift exemption which is so small in this context as to be negligible.
There are two other taxes that do apply on a gift however, capital gains tax and stamp duty, which do not apply on an inheritance. Although certain exemptions can apply and you can, sometimes, make yourself qualify for those exemptions.
More than anything else, planning is key to making sure as little tax as possible is paid legitimately. Ideally your father would talk to a tax adviser and discuss the options.
As above other issues come into it- the possibility of nursing home care being needed, his retaining rights for himself, whether a lifetime transfer is better or a will. Discussing it now with advice can save a great deal of tax.