If it were me I would opt for the 5 year program, over the 6. But that's a matter of preference. I'd rather have one less year of tuition and living expenses.
Liverpool will still give you a quality education as will RCSI.
I used to live in the UK, and I visited a lot places there, albeit never Liverpool, but I've yet to come across a British city that I disliked, although Manchester came close.
I'd say pick the school that is in the location you want to live in most. Both programs will be of high quality, both will make you a doctor, which is the important thing.
Whoah I just checked Atlantic Bridge. RCSI charges €48,000 (approx $62,000) PER YEAR even for the SIX year program! That's outrageous. That extra year at RCSI is going to cost you about $85,000 once you factor in travel, and living expenses, and you're looking at AT LEAST $400,000 going that route.
I'd venture Liverpool has a lower cost of living than Dublin and their medicine tuition is £23,000 ($35,650) per year... That's roughly HALF the price of RCSI. You'd be half mad to pay double price, and stay an extra year, unless your parents are Bill and Melinda Gates!