Troff, the difference is that hold baggage is weighed and has a paper trail, so overweight baggage might be flagged on the system and a surcharge unavoidable, while few companies weigh hand baggage. The check-in staff helped you dodge that, so they are to be commended, not criticised. O'Leary stated on TV that passengers should wear anything that doesn't fit in their hand baggage to avoid using hold baggage and the fees!