[jyl]

My research is about 8 years old (my kids are older) but the five-point harness seats seemed best. The "shield" seats were more convenient but some didn't hold the child securely in accidents. I used the Consumer Reports tests, mostly. As a bonus, there were (maybe still are) some models of five-point seats that fit in the 911 rear seat. Also, the harness type seats will usually be usable as boosters when the child gets older.