It's faster, and the app gives a list of the purchases you've made with a card, so I can track what I'm spending relatively easily. Unfortunately, there are still lots of stores that haven't upgraded to contactless yet, which means I can't rely on Android pay for the time being. I can see this being much worse in Europe where contactless payments aren't implemented in many more places than here in Canada.
A) there is a risk as everyone can create a stripe account and buy a charger. Personally I would never notice.
B) every transaction creates costs. Some visible (depit charging fee) some hidden (credit transaction fee)
C) At least in most of Europe it is far from widely supported, even thought it's growing for a while now. Except you stick to the most touristy places that is. In south east Asia I haven't seen it at all except in tourist focused places.
Personally, the convenience of: not having to wear a wallet at all (I just carry the card in my pocket) and not having to deal with coins, negotiate if I'm paying a big bill etc. is just amazing. Even if someone steals $10 from me once in a blue moon, it's well worth it.
The credit card never really saved me. It really just is there to make life a little easier.
When I tried using my debit card and they ended up taking the money and then refunding it over a week later.
[0]: In contrast to e.g. Rewe which is also mostly operated by independent merchants but has strict rules for those.
Standard on most bank cards in the UK. No pin or anything. Tap it on the machine and you go. Takes 2 seconds at most.
Still, I do hold cash sometimes, you do need it in some cases.