From what I understand Q1900 has been worked on the forum for a while so you might get more support out of it.   Honestly I dont know - depends on your needs. J3455 works good for what I'm using it for - plex, BT, small back-ups.   CPU rarely goes up to 90%, I just got 8GB 1600mhz ram for it too so its smooooooth as butter. My plans to play around with Asterisk.     About the speed, I need to ssh into machine and see CPU stats. I'll let you know whats up.