Well i do apologize as i was only giving an example
It's because the way some Universities look at it, you took two years doing your AS's, so when you apply in your A2 year, many will be skeptical that you can pass your A2's in just one year with good grades - as A2's are so much harder.
Therefore, you may get amazing grades at AS and continue to receive good grades at A2, but on the other hand, the way the University looks at it, there may be many other applicants who achieved good grades in just two years and not three.
Anyway, i'm not saying all Universities do this, but many will judge you on how many years you take resitting and stuff - my friend was rejected from two of his choices due to resitting his AS's, but they were Russel Group Uni's, so i guess that's understandable?
But anyway, it really does depend on what you want to apply to and where eventually. I agree that retaking the year can help you enormously so it's really your decision. I would, personally, retake the year, given the fact that there are no more January exams, so resitting modules along with your A2's would be extremely difficult and stressful!