IPhone 4s to iPhone 6. Data swap?

Will I have to switch sim cards in order to get all my messages and stuff or can I just do it with iPhone backup or both?

Added (1). This is with AT&T btw

Swapping the SIM relates to the phone number, not the data on the phone. The backup yes would transfer the data between the phones.

Just connect to itunes, backup, then when you setup new iphone it copies everything for you. For photos I always like to use windows explorer and just cut/paste to computer so I know I have them all or at least hte ones I want.

ITunes or iCloud backup will do that. Preferably iTunes backup. Activate at home and use the 'set up like a new phone' option in iTunes and attempt to restore from your backup. The sim card won't switch anyway. Two different sizes. Best luck.