Applying for Maths at Oxbridge during gap year

I am currently looking to apply for Maths at either Oxford or Cambridge in my gap year, next year. That means I would have my results in hand.
However, there are some things which I am unsure of
- for Cambridge, do I do STEP this year, or next year in my gap year? how would that work?
- same for Oxford and MAT
- which uni is more favourable to gap years?
- which uni, ultimately, is better for maths?
Not 100% sure at the moment what to do - which one to choose. Naturally I suspect maybe it's down to personal choice, but would appreciate some pointers,

I am currently looking to apply for Maths at either Oxford or Cambridge in my gap year, next year. That means I would have my results in hand.
However, there are some things which I am unsure of
- for Cambridge, do I do STEP this year, or next year in my gap year? how would that work?
- same for Oxford and MAT
- which uni is more favourable to gap years?
- which uni, ultimately, is better for maths?
Not 100% sure at the moment what to do - which one to choose. Naturally I suspect maybe it's down to personal choice, but would appreciate some pointers,

I applied to Cambridge for Maths during my gap year.
1) You can do it in the same year as your A-Levels, it's up to you. If you do it at the same time as your A-Levels, then you would have to deal with the workload of doing both and it is possible that some colleges would ask you to do it again during year gap year. However, it may be a convincing sign of your ability if you were to already have it at the point of application (and some colleges would be satisfied with your doing it once). Also note that sometimes, gap year applicants who apply during their gap years are asked for a higher STEP grade, often S,1 for gap year applicants compared to 1,1 for others.
2) I'm not certain but I think the MAT is only valid for the year you apply for unless you're doing deferred entry. Someone at Oxford would have to clarify this.
3) Not sure, it may depend on the colleges. At Cambridge, some colleges have distinctly different attitudes towards deferred entry applicants but I don't know how this translates to those who apply during their gap years.
4) Matter of opinion.