I have used both. RBF is pretty straight forward. CPFP is a little trickier because you have to get two transactions through when you use it, so you need to do the math to make sure that you are paying enough sats / byte to get both into a block. For example:

I fat finger a transaction and submit with 1 sat/byte. I use CPFP to make a new transaction at 10 sats/byte, thinking that will suffice as mempool fees are around 8 sats/byte in this example. However, i did not do the math! Because i need to pay for two transactions ( thus twice the space in the next block ) my effective rate is ends up around 5 sats/byte leaving me still unable to get my transaction confirmed. I could then do another CPFP but now i have 3 transactions to pull through into the next block... so i better do the math right this time.

CPFP also comes from the change of your broadcasted transaction, meaning you cant do it for a utxo where you send all or almost all of the sats.