Travelling next summer - Take 1 big rucksack or a suitcase?

I went to Australia for a few months with a backpack, but ended up swapping it for a suitcase because I somehow had too much stuff . But it was my first time bacpacking and in general I tend to be too much of an overpacker, so I'm hoping next time I go backpacking I try sticking with a backpack the whole way, as it would be a lot easier with moving about frequently. A suitcase is better if you really need to take lots of stuff, but of course it'll be heavier and a bit less mobile than a backpack, so those are the sort of things you need to think about. And if you're only away for a couple of weeks, it's a lot easier to get away with taking less stuff and not missing your whole wardrobe for too long if you're quite fashion conscious like me , so in your case I'd probably recommend a backpack.

It's up to you at the end of the day though, as there are always mixed opinions about this on travel sites, since everyone has their preferences!

I went inter-railing for 3 weeks with this notion that I needed a rucksack... retrospectively I would have taken a wheelie suitcase! If you've got somewhere like a hotel to leave your stuff during the day instead of needing to carry it with you all the time, AND you're going to be in paved/urban areas when you do have your luggage... then wheelie suitcase all the way! It's so much more practical than murdering your back trying to get your stuff from the train to the hotel and back every time you move on.