Garmin Edge 500/510 vs. Powertap Joule GPS

I currently have an older Joule bike computer (gray and yellow) and I am considering upgrading to a GPS computer. I have been doing quite a bit of reading and I narrowed my selection down to the Garmin Edge 500, the Garmin Edge 510 and the Powertap Joule GPS.
I am already familiar with the Joule dashboards, which I like a little bit more than the Garmin, since I can see more metrics on the same screen. I am now try to understand the differences between the computers in the navigation part, specifically in the ability to load and follow routes. I went through the manuals of all of them and, while I am quite clear on the capabilities of the Joule GPS, both Garmin manuals seem to have a pretty scarce amount of information about this.

What I know so far:

  1. None of these devices supports maps, which is OK for me.
  2. You can upload externally planned/downloaded routes on the Joule GPS in various formats (TCX, GPX).

What I don’t know:

  1. Can you also upload externally planned/downloaded routes to the 500/510?
  2. The Garmin website seems to suggest that both models support 0 routes? What does this mean?
  3. If yes, what formats can you upload, i.e. can you get routes from any website in standard format or only through Garmin Connect?
  4. What are the significant differences in this regard between the two models (and yes, I have used the comparison feature on the website)?

Any other thoughts people have about what they like/dislike in those bike computers?
Thanks!

You can load GPS routes to the 500, but mine is really unreliable when you try to follow them. The screen keeps going blank while it recalculates. Makes it pretty useless. I seem to remember it being said that this was due to lack of processing power, so the 510 maybe ok.

Maybe others find it works ok?

One thing to keep in mind if you use poweagent is that the joule files will import directly, whereas the garmin files require the use of a separate program to convert to tcx before import.

I do really like that the garmin 500 interface is so similar to my 910’s.

I am already familiar with the Joule dashboards, which I like a little bit more than the Garmin, since I can see more metrics on the same screen.

How many metrics can you see on screen at once on the Joule? The Garmin 510 allows you to display up to 10.

Ok fair enough, maybe I wasn’t overly clear. You can really see 8 metrics at the same time. However, here’s the trick. Of those 8, 6 are fixed and 2 are variable. In other words, as you highlight any of the 6, you will see 2 additional ones on the bottom line.
E.g. you might want to typically see current power and HR. If you highlight current power, you might configure the two bottom metrics to be average and max power. If you highlight current HR, you will now see average and max HR and so on. I do have a mild preference for this vs. having to entirely switch dashboards.

510 works well with externally planned routes for turn by turn but obviously no real map feature. I went from a 500 to 510 and there is a definite decrease in battery life in the 510. Another option which isn’t yet available but will be very soon is the new SRM Power Control 8.