Horizons starts explaining problems in the student book in grade 4. ABeka starts this earlier. Both programs are not complete without the TM and should be judged as a whole program and not just a wb. Horizons TM includes student directions in K-3. IMHO both are solid, spiral programs, in a colorful workbook format, with lots of review.
Problem solving is included in both.
I don't keep grades but she likes to take the tests and consistently scores 90 and above. If so, please let me know which you preferred and why. I really like ABeka. ABeka is a soild, spiral program. It has the review my DD needs.