What's in the phone has absolutely nothing to do with the SIM, so as B. Diddy said, it doesn't matter. Switch the SIM, then transfer thew content, or transfer the content, then switch the SIM. The only difference it makes is, if you get a phone call or text, which phone it goes to (the one with the SIM) - so maybe it's better to turn on airplane mode in both phones first, doi the copying and SIM swap in whatever order you like, then turn off airplane mode. (If you get a text in a phone you're taking the SIM out of, it's going to be difficult to respond to it with the other phone, after you switch the SIM. If you get a text on the Galaxy, then swap the data, you've wiped out that text.)