My main problem with crypto merchants is a lot of the time they charge more than paying with your local currency, like it's some type of honour.
I have also noticed that some stores have expressed prices in fiat and crypto, but paying with BTC is in many cases somewhat more expensive. In this case, even though the merchant accepts BTC as a payment method, it still encourages the buyer to pay in fiat. I asked a merchant in my country why it was more expensive to pay at BTC, and he replied that he is just traying to protect himself from sudden price changes. But he actually uses a payment processor to protect him from the same problem, so the situation is a bit absurd. I think paying with crypto is still a good way to avoid paying taxes (except VAT), and that merchant playing on that card.
OP paying with crypto can be very good sometimes, for example, if you buy BTC just a year ago for $3000 or $4000, value of those coins are go up 100% and you get more for your crypto. In case you buy BTC now and then use that crypto to pay for something, it probably won't bring you any benefits in terms of a cheaper price. However, I personally prefer to pay in BTC whenever possible, I see it as my small contribution to the promotion and adaptation of cryptocurrency.