FWIW, I don't like to use tabs because I tend to forget where I've buried some then when you uproot/replant there's issues with how much is released into the water column. Some plants may need them, but they're not the ones I'm growing.
I use both... Most plants take nutrients from the water column so the liquid ferts work for these plants. If you have plants like Swords & Crypts you will want to use root tabs, these plants feed heavily from their roots.
Do crypts and swords feed heavily from the roots because the water column is insufficient? I was led to believe plants will take nutrients from the water column first as it cuts down on energy loss of having to transfer nutrients through thte plant.
Yeah, Tom reminds us regularly that substrate ferts aren't needed. I agree with him but personally I have had better results using both so I keep doing so. They are worth a try, if anything they will help balance out any eventual deficiencies in your water column fertilization.