I own both of them right now and I think there is a noticable difference in overall detail and clarity between the 3G and 5G. Also, with my Ety ER4Ss, the soundstage is much more precise with the 5G. I'm using an RnB line-out cable with a Hornet.
I tried rockbox for a few days but it wasn't really working for me so I switched back to the standard firmware. However, I didn't notice any difference in SQ between files of the same format.