no difference apart that if you enrol outside of university you can choose to pay to those classes that you are interested on instead of just taking whatver the uni offered you. You can choose your teachers too. This gives the  student a very high bargaining power. So choose based on quality becomes a norm in non-uni centres. Just imagine a housewife running to 5 different hypermarkets to get the best discount you will get the picture.

for tarc you will have to go for diploma(2 years 4 months) then advanced diploma cum ACCA(1 years 8 months)
with the advanced diploma,you are exempted 9 papers for ACCA which left you 5 more papers.
So total time estimated should be around 5 years provided you pass all the ACCA papers.