Where to register a new car

U_Fig

I was chatting to a mate of mine today about cars and stuff during lunch and he was filling me in on his situation and just asked my opinion on a couple of things. So i said i'd post here to see if anyone had been in a similar substation or have an option on what to do. i'm not overly sure on the best option

A bit of background on my mate, lets call him "Dave" for simplicity.

Dave is originally from the North where he owns a house but for the past 15 years has worked for a Company based in Dublin as a rep on the road (all in the south) and has a Company Car (Audi A4 Diesel)

He Owns an apartment in Dublin region and stays there for maybe 3-5 days a week (3 days most weeks but can be 5 depending on the week) and then drives back to his Family in the North at the weekends or if he has time off

He is now moving internally to an office based Job and as a result will give up the Company Car and go on mileage for any business use of his personal car.

He is buying a new car and is caught about registering it in the North vs the South.

He is looking on buying something like an AUDI S4 / RS4 or from bout 2009-2012 as him mileage will be low enough and he loves fast Audis and newer ones are out of budget.

Financially it makes sense to register this as a Northern Car at his home address due to tax reasons but would this cause any issues being down in Dublin for a minimum of 3 days a week and sometimes 5 even though he has a northern address?

Lantus

Assuming dave is paid in euros he is classed as tax resident in the South. Living in the south for on average more than half the week and therefore year is also classed as being resident in South.

He should have a southern driving license surely?