People going on record attempts around the whole of the British Isles normally do it anticlockwise on the grounds of having more chance of favourable winds in the typical depressionary systems we have. I don't know if this logic would still hold good on the smaller circuit of Ireland alone.
We tried it anti-clockwise 3 years ago, but got stuck at Portrush waiting for suitable weather to get around Malin Head. The winds were W to NW 4-6 and so gave us bad 'wind over tide' conditions for this tricky headland.
In the end we back tracked down the E coast instead.
clockwise - if you get the tide right in the irish sea its worth six to eight knots, the south coast has plenty of good harbours, bars restaurants etc. Sailed from Crosshaven in Cork to Dun Laoghaire two weeks ago (anti clockwise) 8 hour spinaker run from Crosshaven to Hook Head. It depends on how long you want to take and where on the west coast you are heading for.
Nick has a point. Yes both ways. Reeds Almanac covers Ireland. There is a seperate Irish edition from the ISA they are at www.sailing.ie. It has tidal streams, etc. With you with a boat speed of 6knots is 6+6 over land, against put down anchor and make tea.