As others have pointed out all the more reason to check the original sources. With Griffiths on the Ask about Ireland site being so friendly and fascinating there is little reason to go any other site where the possibility exists of double transcriptions leading to double the errors.
OP you have said you want to see what triggered a move from Co Roscommon to Co Clare or vice versa by members of the O'Brien family. Rather than trying to find it in individual documents have you looked at broad histories ie what was happening for the populace at the time? It may be some thing like a change of landlord, merging of tenants properties, famine & poor crops as well as the more personal ones such as a son marrying into a family from that area, the wider family owning land there.
What were the dates that you think the move took place and was it a whole family or one family?
The other good thing about using GV on the original site is that you can see the original published entries and work out from them the system of leases and subleases ie the LL may lease to John Brown and then John brown subleases to several others. You can also see who else was living in the same townland by looking at the Griffiths Places search. That is a very powerful tool as families often married into families close by and you can often find them on this part of GV
