At the moment I have both. Won't go into why
(Think D*TV Garbage)
Anyways...My perceptions of the differences - these are my opinions and you may or may not expereince the same....(disclaimer in place
520 outputs 480/480i, 720, 1080i
E86 outputs 480/1080
E86 will not output 480 on component - 520 does (although it looks pretty bad), but makes it easier if you are surfing around so that you do not have to go throughy the change aspect/output/input/hd-sd stuff.
E86 & 520 HD output on 1080 were identical on my system with no perceiveable differences in PQ
E86 SD S-Video ouput was better than the 520 s-video output - namely less color push, sharper picture, less artifacts
E86/520 composite output was pretty close, perhaps a slight edge to the 520 - but only slight
520 has DVI ouput/E86 does not
Either one of these are not really easy for a non day to day user to get changing from HD to SD, picking the right aspect, changing inputs on your display(if necessary) etc. The 520 has a slight edge in that it has several modes such as native and hybrid that allow you to leave it there and the STB will handle all the switching etc(this would either be via component or DVI - or using a A/V receiver that allows multiple inputs and upconvers like the denon 3803). This comes at a cost - as the SD PQ is not really all that good fed via component. (I have not tried DVI yet) or S-video. But suffices for surfing.
Using a Zenith siver senser antenna - connected to the E86, I received NO hd stations in my area. (I live way out of town). Using same antenna in same location with the 520 - got 6 HD stations OTA. (YEA!!!!!) It appears the 520 has a better capability to "grab" and hang onto a signal.That alone made it a keeper for me.
The E86 Remote is about 1000X better than the 520 remote which is simply impossible to operate. I have a Harmony 768 Universal remote and was playing around with it controlling all my STB functions. That playing stopped the second I ended up with the 520, immediately figured out how to program what I needed as the 520 remote is horrible. Do not think you will be able to live with the 520 remote unless you have 10in fingers or want to use two hands all the time.
The 520 has a display that shows the station and an indicator of the signal. The E86 does not. For me no display is actually a feature
As all my equipment is in front of me and I'm tired of glowing lights!
The E86 has caller ID - I really do miss this...has a better guide (as in much better) - the 520 guide covers the whole screen and when you change channels you have to force it to go away or wait! The E86 also has better options for setting the guide etc. I do like surf on the 520 better than the equivalent function on the Hughes.
If you have to have DVI - no brainer - 520
The other points you will need to evaluate for your needs. Lots of folks have had great success with getting the E86 for OTA stations. Keep in mind I am in the boonies and did not expect to get OTA - the fact that the 520 did is amazing - but my experience should not be used as an indicator.
After this weekend, I have decided to keep the 520 and sell the E86. PLease note that there is a software rev level of 1.02 that should be on the 520 and if not there getting it downloaded from DTV is not a trivial affair. On the same note I have been having download problems with DTV on the Hughes as well. SO this was not a show stopper for me.