I’m not referring to which state your finances should be in, that is rather obvious. Instead, I’m talking about credit cards and debit cards.
When in Britain, the answer was nearly always obvious - using my Switch (now Maestro) card made more sense, as I could only spend what I actually had (I specifically asked for no overdraft on my bank account), and there were no fees involved. If I needed to immediately buy an expensive item, and would not get paid for a couple of weeks, then a credit card could help bridge the gap.
However, when it comes to spending money internationally, matters are complicated somewhat. It certainly makes sense to compare credit cards from different companies, as some charge more than others for overseas purchases; combine that with the fact that most shops in Kazakhstan do not accept Maestro, and you need to make sure you have the right card with you when you go out. Of course, if you already have a credit card and wish to swap, then the balance transfers available in the current market could well swing your decision as to which company to give your business to.