Stay rear facing. The aap recently recommended that babies remain rear facing until at least 2 yrs, or later if under the maximum weight for that seat. Car seats with "side impact protection" are being marketed but there is not yet standard testing for this feature. If possible, the middle of the back seat is safest. Booster seats are for after 4 yrs or 40# (whichever later), but many car seats accommodate 100#.
Booster seats. It is recommended for babies to stay backwards in their infant car seats for 2 yrs & 30 lbs or the maximum of your car seat (found on a sticker on the side of the seat). When they reach these limits, turn the toddler forward in a forward facing car seat with harness until 4 years and 40 pounds, then a booster seat with seatbelt until 4 ft 9. For more info: http://www.Statehighwaysafety.Org.
Answer varies. The 5 point harness system is accepted by experts as providing the most protection thru a variety of crash settings. Fph seats are available for birth to 85 lb as infant, convertable or forward only models. Rear facing is preferred for neck protection until two or later. Boosters help in older kids but are less help in roll overs. Brand matters less than your confort in knowing how to use it.