Y is the way to go because only 14% of people in the UK share my Y Chromosome it is easy to eliminate all of the R1B’s with the same last name. It also helps to have a place to start, in my case I had seven generations in one town so that hitting the local Historical groups helps.
The upside is that they were prominent, in some cases, the down side is they bred like rats.
>> The problem with MT DNA and your mother is Irish you can get a match but finding a relationship before 1800 is very difficult <<
Absolutely correct, due especially to the fact that in our society, women have for hundreds of years taken their husbands surnames, meaning that the surname changes with every generation. That pattern makes it much more difficult to use mtDNA matching than it is to use Y-DNA matching.
Still, you can occasionally hit paydirt with an mtDNA match. So as long as somebody can afford the expense, I recommend that he or she get an mtDNA test.