Which arduino should i use?

Hello, i have a school project and i choose to do a smartwatch. It won't have many features, i was thinking for sms/call notifications, change song, show clock and I'm going to connect it with a phone which it will recive the notifications etc. My question is, which arduino should i use for this typical project? Me and my group are talking about arduino mini pro or arduino nano. Which one is better? And if there is any other which is better for this project feel free to say so :)

the nano has on-board USB, the mini pro has it as a separate part.

check the parts needed for the interface to the sms and such. that will reveal the answer.