We started the year with Saxon, and my 10YO, who is very good in math, really didn’t like Saxon. There were tears every day.
We switched to TT in October and I am VERY happy with it. I do think it is generally a grade behind (so TT5 would really be 4th grade, etc.) My 4th grader, who excels at math, is doing TT7 (which I would consider a 6th grade program).
One complaint I have heard about TT is that it does not have as many review problems as some of the other traditional math texts, especially Saxon. For us, though, the sheer number of review problems in Saxon is one thing that frustrated my DS.
Don’t forget that the TT website has sample lessons for each grade level that you can do right from their web site. That might help you with your decision.