Bitcoin is slow - it takes minimum 10 mins with high fees, or in times of congestion, hours or days with low fees. Faster payments takes minimum a few seconds, maximum 2 hours, for processing, no fees involved.
Bitcoin is expensive - fees are variable depending on congestion on the network, and current value of BTC. Faster Payments charge nothing to transfer 0.01 - 100,000.00 GBP (in reality, 10k - 100k, depending on your bank. I have banks that allow 25k and 50k) in a single transaction.
Bitcoin is a wonderful experiment, wonderful proof of trustless immutable transactions, but as far as a payment system goes, is only better in one way, and worse in many others.