I've spent some more time with the 5100, and I have come to the conclusion that overall stability seems to be better.
For example when watching a video on youtube using the new youtube app introduced with the last firmware update on the 590, the video kept stalling and restarting. The same video on the 5100 with latest firmware played without pauses. Another thing I noticed, is when you have a usb device connected, the player seems to recognize what type of device it is. In my case I got two usb SD card readers that can plug directly in, and on the 5100 it recognized it was a card reader. On the 590, it just says Usb device (front) or (back) whichever it's plugged into. Also like the new Facebook app, interface. I have to say I like the smaller case design of the 5100 as well. I've decided to connect the soundbar and connect the new unit by HDMI to living room tv. I like the results after adjusting tv sound settings and turning on surround on the TV, and surround on, in the audio down mix settings of the player. The picture is great, the player is quiet, and very stable. I am overall satisfied with the upgrade after I took some time to in detail compare the two units.