android 5.1 vs 4.4.4 and question on text and navi use

Hi All,

I am debating on weather to get the android 5.1 or the 4.4.4 navigation head unit. Any thoughts ? and how much ram and memory should I have in the unit.

For those that already have the unit, does it allow for navigation use while driving ? vs having to stop to put in destinations ?

On text messaging, does the unit allow for you to answer text messages while driving and does it have pre programmed text answers ?

thanks in advance !!