do you know any PPA having retroarch armhf packages for Ubuntu?
Many ARM devices can run both Android and vanilla Linux. Do you think i will get better performances using retroarch in vanilla Linux instead of the Android version?
RetroArch on ARM Linux would get you better performance than Android yeah (probably a lot better since most of the stalls come from the JVM garbage collector) - provided that you have mature and working video/audio/input drivers (not all of which are a given on most devices for which there is an ARM Linux distro available)
Just as i thought… 
Some real-numbers comparison would be interesting…