Early entry and all forms of acceleration are such individual decisions, that is why they are so hard. No two person's circumstances, or children, are exactly the same. What works for one child doesn't necessarily work for another. Kids draw contentment from different things, being a leader, playing sports with age peers, playing in an adult orchestra, working on higher level academics.
Even with all the positive research on acceleration it all comes down to each particular child in the end and what they need.
Having IQ data can be very helpful both to indicate a level of giftedness or different learning profiles. But it is just one piece of the puzzle. And as we have seen, no two IQ tests measure exactly the same things. It is reasonable to work out what test best suits your child and circumstance. Good luck finding an answer Jayta. We had trouble getting the SB V when we wanted it.
Even with what you think is the best test, sometimes the result I doesn't match up with what you know about your child. Then it comes back to knowing your DC best. Again, really hard. We are intelligent people trying to make difficult decisions for our important little beings. We like hard facts and data to guide us but sometimes it just isn't there.
But all information is good information. I too can get frustrated by people with anecdotes against acceleration but I have to remember, take away anything that is valuable from the story and note that their decision worked for them. It's like case reports in medicine. Sometimes situations, illnesses, reactions to treatment are so rare that there isn't anything but case reports to rely upon. But then population data doesn't necessarily help work out what will happen to any one individual either.
Our situations are unique enough that it's hard to find anyone in exactly the same position. Even here. But there are enough similarities to get good advice.
