It looks like an nice bag. But to be honest I never bothered with a special changing bag. I looked at loads of different ones and in the end never got around to getting one before dd was born. Then after I decided to use my own back pack as it was a trendy one that I loved to use before dd. Also used an airline toiletry bag to keep all the little bits and pieces in.
Its up to you but if you have a spacious bag you already like then I'd use that.
I guess if you are going to use reusable nappies a bag with a space for them might be useful but nappy sacks usually work well.