Both are equally safe when used correctly.
Most people don’t realize that the LATCH (Lower Anchors and Tethers for CHildren) has a maximum weight recommendation, so it’s important to look in your owner’s manual to know what your vehicle recommends.
Note that the weight recommendation is the weight of the carseat PLUS the weight of the child. It is also important to note that most vehicles have a LATCH behind both the passenger and driver’s seats but NOT in the center. Do not use the middle LATCH from each side to anchor a car seat in the middle! Instead use the regular middle car seat belt.
When using LATCH, make sure to also use the top tether if you have an anchor in back of the seat.