I've lived in 2 flats in halls and had both. Different unis, so as far as cost goes i can't comment; my ensuite room was cheaper than my shared bathroom room, but they were in different cities. In general shared bathroom is cheaper.
Ensuite was good, particularly when i got sick and needed to throw up every 5 minutes. Getting ready in the morning without having to leave my room was great! But my flat, which was 8 people, mixed gender, got pretty antisocial and we ended up never speaking because everyone just stayed in their rooms constantly.
My other flat was 5 girls, and we had 2 toilets and one shower. I never had any issues waiting, but we had to clean it ourselves and some of the girls were much messier than others and would typically refuse to clean it. Nothing quite like having to scrape someone else's **** off a toilet because all 4 of your flatmates apparently never use that one and don't want to clean it. I think in most places though shared bathrooms are cleaned for you.
Also, if you can't stand the thought of sharing; remember that unless you stay in halls for your entire degree, you're unlikely to get an ensuite in your house after halls. Sharing now with horrible, messy, time consuming people makes the transition to living with a smaller group much more bearable!
...with these A Level results?