From my understanding a both types of Commissioner perform the same function under law - taking swearing and affidavits. There may be differences and, is so, I'm not aware of what they are.
Yes, it looks like you are correct. Order 40 of the Rules of the Superior Courts states:I don't believe a Peace Commissioner can swear an affidavid - you would need a Commissioner of Oaths for this. However, they can witness documents. Also, they have the authority to issue summons and search warrants to Gardai (infrequently used) - I don't think Commissioners for Oaths can do this.
Peace Commissioners are not supposed to charge. Commissioners for Oaths can charge (although if they happen also to be a Peace Commissioner they are not supposed to charge for simply witnessing documents).
Peace Commissioner - Wikipedia
en.wikipedia.org
Thanks for that but I have been charged by a Peace Commissioner on numerous occasions for signing a document or similar. On getting the service done I would say, do I owe you anything? and the answer was "Ah sure a tenner will cover it". Anyone else have similar experiences?