When you download a game, what matters more : 
1. Get to play as soon as possible, so like a guest mode
2. Your data being saved properly so you don't lose it in case you delete or lose your device.

building /chaincade /xd | memes are on hiatus

I always just assume that game data will not transfer to a new device.

Yes, my assumption for most games is that if I start playing it on a particular device, I will only be able to pick up that game if I continue to use the same device. If I want to use something else I would have to start over.

As a general rule, not an absolute.