Ipod storage vs Iphone storage issue

[jdogcarroll]

So I just bought an ipod 6th gen today (same 16gb as my iphone) but I noticed spotify the app and all of my offline data takes up alost double the storage as it does on my iphone (10.4gb on my ipod and 5.5gb on my iphone)... Can someone explain this? I was trying to download all my songs but it coudn't do them because it ran out of room on my ipod. To be honest I have not been very happy about this ipod since I bought it and was wondering if it is an ipod thing or a setting somewhere. Thanks in advance!!