Google +sign in qwestion about more then one base

If I have 2 clash of clans bases. a base synced to my gmail and my main base I use is synced to my hotmail. I was useing my old phone, connect it to my wifi for my other base I used. Phone broke so so the qwestion is ...on the settings where it has the Google+sign in. If I choose my other base it says progress in game will be lost. What is it exactly I loose???? My troops just made? My gem boosts I just did? My lat few raids I did and collected gold n such???????