You could go by the stats from the 2011 birthplace study.
If you're low risk and it's your first baby, the overall safest place (for both baby and mother health) is a standalone midwife led birth centre, followed by a midwife led unit attached to a hospital, followed by a consultant unit, followed by home birth. There's not much risk difference between the first three, but the rate of interventions (and maternal complications and recovery time) increases with each one. Home births for first-time mothers have a higher risk for the baby, which is probably less important if you're 5 mins from a hospital than if you're over an hour away.
If you're low risk and it's your second or subsequent baby, the overall safest place is home, followed by standalone midwife led birth centre, followed by a midwife led unit attached to a hospital, followed by a consultant unit. There's not much difference between the first two, as home births are very safe for mothers that are low-risk the second time round (i.e., they've already had a straightforward birth).
After that, it's personal preference. If you're the kind of person who is reassured by doctors and NICU being close by, then you might feel safest and have an easier birth in a hospital consultant unit. But if you're the kind of person who finds hospital environments stressful, then you might feel safest and have an easier birth in a standalone birth centre (or at home).
Talk to your midwife, know the relative risks, visit the options to get an idea of where suits you best, and pick somewhere that makes you feel safe and comfortable 