It may be the case that Tiffin is harder to get into due to the fact that fewer will sit the exams for KGS (or Hampton for that matter, though about 650 boys sit the Hampton entrance exam for 125 places so still a 5:1 ratio of boys to places). It is certainly also true that many will sit the Tiffin exam with no intention whatsoever of attending, and many will sit in hope rather than expectation, after all what do you have to lose considering it is free? Whichever way you look at it, all these tests are difficult, and any child will have done well to pass them. Which is "more difficult" might just depend on what your child finds easier and how that matches to a particular test, and also just whether they have a good or a bad day.
As for where those children eventually attend and how this can be read as an indicator for which is harder/better, well one poster suggested that as most of a Tiffin class had passed Wilsons and Sutton Grammar but attended Tiffin instead we should "do the maths" and work that out. The problem with this maths is that it doesn't factor in that Wilsons is over 8 miles as the crow flies away from Tiffin, and factoring in morning traffic there is a very small band of children that live in an area that would be able to attend Wilsons that end up at Tiffin. Most of those in that Tiffin class would live too far away to ever think of going to Wilsons. I live almost equidistant between the two, and although our son passed to allow us to put Wilsons on the CAF we didn't consider it because it was just too much of a pain to get to. Given an equal choice not based on travel we'd have chosen Wilsons over Tiffin due to the onsite playing fields and the better academic record. Certainly many I know have rejected Tiffin for other schools for many reasons, just as many have rejected KGS/SGS/Hampton for Tiffin.
What I would think about is that no matter how hard the exam is, getting into the school is not your end point, either academically or in development of a rounded person. Whilst the latter is difficult to measure, public exam results do allow us to measure the former. All schools mentioned perform very well, but it intrigues me that if Tiffin exam is much harder and they take in the academic "cream" at 11+, what are KGS, Hampton and indeed Wilsons doing so much better that they all outperform Tiffin at GCSE results? (%age entries achieving A/A) According to The Times Parent Power table 2017 results, Tiffin achieved 78.5% GCSEs at A/A, KGS 87.3%, Wilsons 86.1% and Hampton 93.4% If you factor in A-levels (where Tiffin does a little better than KGS) the two schools are almost inseparable on academic record.
So to return to the salient point, yes you have to be pretty bright, but you never know until you try, and what do you have to lose? Nothing ventured nothing gained as they say, and whilst it seems that Tiffin may be more difficult to get into than KGS, academically your child is likely to achieve as well at either establishment. Given that, it is probably best not to choose KGS because "you get what you pay for" or Tiffin because "it is harder to get into therefore more exclusive and better". Enter both, see how your son gets on, and if you are lucky enough to have to make a choice then it is likely to be on other factors than how hard the exam was! Good luck!
