Originally Posted by
achoo
What makes you think a flat bars are going to be more comfortable than drop bars given the geometry of the bike won't change?
To be fair OP never mentioned anything about comfort other than asking if carbon, alum or titanium bars would be more comfortable than another.
But seriously, Pacer with 105 is a nice bike. If OP wants flat bars I would sell that bike and buy a hybrid. Probably get enough in the sale of the Pacer to pay for a decent hybrid as they are cheaper than road bikes