If you have a Google account, it's a good idea to move your contacts over so that they're backed up and will sync with any new device the moment you sign in. It's possible to have either device or Google conatcts, or both, but Google is better, really. I've never used an Android device without a Google account, so don't know what it would do to basic settings - the nearest I've come is setting a phone up on wifi and then inserting a SIM, at which point my homescreens reverted to default (but I think that was all). That was a long time ago and it may not happen now, or have been brand-specific.
As well as keeping my contacts on Google, I also periodically export them and back that file up in as many places as possible.
