I must admit that lots of programs stores numerical values in textual form but I can't understand why. Sure it is good to be able to see some of theese values outside the program sometimes but in most times you wouldn't want those values to be so easy accsesible since changing any of those can have huge impact on your program.
Also converting values from textual form and back is quite slow process. Textual representation of theese values usually takes more space to store. And finally the sligthest data corruption (one letter inserted in the value) and you get that nasty "String conversion fail" Exception which would deffinitly scare many customers away from using your programs. Nobody likes seeing Exception windows poping up in your applications.

So personally I avoid storing any numerical value in textual form.
I also try avoiding the use of XML files. Sure the original idea of XML is to make filetype which would alow sharing information stored in it between different applications and even systems. But reality is that XML is far from that. If you are monitoring other general programing forums you can see that quite some peepole are having problems of extracting the data from XML files they got somwhere around the web. Finally many of them solves their problem by hardcoding the data structure of XML file into their program despite the fact that every XML should already contain the necessary information to get the data structure out of it automaticly.