The psychiatry route offers a lot more certainty and career progression. For that route the issue is getting into medical school, as once you are past that barrier things are very straight forward and mapped out for you to get to consultant grade. Due to the massive shortage of psychiatrist (and even fewer awesome psychiatrists) you are going to be in high demand.
For clinical psychology, the bottleneck starts after you graduate from your undergrad degree. The route to getting onto clinical training is really competitive and not that clear or guaranteed. Once you get onto the doctorate, things get a a lot better, but making the jump from Band 8a (Senior Psychologist) to consultant grade is a lot harder, as there are very few posts.
The roles are very different though, especially in the NHS where psychiatrists roles are far more circumscribed, and if you can spend some time in settings observing both disciplines I would strongly recommend it.