My ds is at Trinity and I know children in a couple of years at RR so I will answer what I can!!!
Class sizes - at T these are about 22, at RR 20-22 - both depend on the year group.
Pastoral care - I think T is pretty good on this score, ds had a couple of "incidents" and they were very well dealt with. RR has a good reputation on this score but, honestly, so much of it depends on the other children in the year. Both schools have form time first thing each day and form tutors are very accessible.
Special needs - okay, can't comment on RR on this one as I don't know anyone who fits in that category at the school. At T, ds has a boy with dyslexia in his class and the school allowed him to drop a language early and he has had extra support. There is also a boy with organisational difficulties (I don't really understand what this means, I'm afraid!) who has received support.
Statemented children - umm, T has a reputation for avoiding statemented children but I don't know how true that is - Whitgift is known to be better in that area.
13+ entry at T tends to be between 12 and 16 or so. No idea at RR, I'm afraid. At 11+ T takes anything anything up to 80 or so, I think, depending on the size of the Junior Form. RR is taking around 80 into Y7 this September.
I can give you the year totals at T as at summer 2012: J 44; 1st 106; 2nd 148; 3rd 149; 4th 136; 5th 134; L6 144; and U6 90. The two "odd" years are 2nd Form and U6 - 2nd Form is much bigger than usual as they took an extra class when they joined the 1st Form as they had too many acceptances! Actually looking at it, 1st Form looks smaller than usual - no idea what happened there. L6 is the first co-ed year which is why it is much bigger than U6.
No doubt late intakes happen - again it depends on the size of the year and what your child can offer.
Ds loves T and I'm amazed at what he has learnt. He is not even remotely at the top of his class and is actually in one of the lowest Maths sets so he will never set the world on fire academically but he enjoys school, is progressing well and has great friends. I was afraid that being with clever boys would leave him deflated but, in fact, it drives him to try harder.
Meanwhile, the children I know at RR love it too. It is horses for courses really. Good luck!!!!