Both RSCI and TCD are great ... TCD is the better however.
Both benefit from being in a capital city and having well funded research, and large city hospitals to work in. St James is the largest and best public hospital in Ireland, and its intensive care facilities are second to none (if you are sick enough to merit getting in that is, - just not enough beds, at EUR 4000 a day!).
The number of places available for non-European students is large in the UK, so I am not sure which has access to the best candidate pool.
Social life in both will be excellent. Both have very contained campuses, meaning that they are hothouses for students. The city now is hugely cosmopolitan, and that is reflected in the hospitals (many of the staff are foreign, although patients, generally elderly, will be almost wholly Irish).
Dublin offers all the advantages of a capital city... so big names on tour tend to drop in. In my experience, its social life if clearly superior to any British provincial city. And while it can't with London for breadth, it makes up for it in concentration. Also bear in mind that the airport is nearby and flights now are cheap - key for internationals. Even AerLingus now has direct flights to Dubai.
TCD does provide accommodation - 1st years are out in Darty, a nice leafy suburb that is a 15 minute back ride away, 45m walking, 15m by tram.
The rooms and appartments provided within TCD are amazing, but can probably only get one year.
Don't know about RSCI.
In the private sector, like in the UK, best value accommodation is in shared 3/4 bedroom houses. Prices vary hugely from area to area, mostly as a function of schools and "standing", neither of which will interest students mcuh per se. For a room in a shared house, maybe most would pay EUR400 to 700 a month.
Both TCD and RSCI are close to the newish DART tram lines (comes close to Darty also).
RSCI just does health-related studies - TCD teaches most disciplines, so meet a wider range of people, although medics too often stay to themselves.
Don't be afraid of meeting people... you'll find it amazingly easy! Indeed in Ireland, you have to make less efforts as small chat is the number one past time...