I've been using Cyclemeter on the iPhone with and without a RFLKT+ for several years and I also have an Edge 1000. With the ANT+ bridge, I've been able to actually use both concurrently using the same sensors to judge their relative accuracy and performance. Bike computing is a bit of an art no matter what because of things like happy (as you note) and wheel size measurements etc...

What I will tell you is that the cadence and speed measurements are pretty much exactly the same when accounting for different display and update rates. I find that there is very little difference between the two systems, maybe a few percent or so. It's not significant given the other errors in the system. The elevation gain when using a barometric sensor such as provided by the RFLKT+ means that they show just about the same gain - again, it's as accurate as a barometric sensor can be and you will find a higher percentage of error at lower elevations in either case. For what it's worth they both seem to be just about the same and they agree reasonably well with calculated approaches in mapping.

At this point, I don't think there is a substantial difference between the phone approach and the standalone GPS approach. With the phone approach - for sure a major advantage when using the phone display is the UI is much, much better. The software also seems to be more reliable than is (in my case) Garmin's.

Finally, if you want to connectivity to inform others of your progress on your ride; a feature I view as a very real safety advantage if you ride alone, the phone wins hands down since the standalone GPS needs to connect to a phone for connectivity anyhow. Then there is the issue of the absolute crap connection that Garmin makes to the phone over bluetooth. It's so annoyingly bad and is being continually dropped with the resulting error display. It so bad that it just gets turned off and is generally unusable.

With the phone approach you also get to choose the feature set you want. If you want an external display, you can do it. If you want to have a better display, you have it with the phone. More battery power? Use a battery sled case (I like iBattz) or an external cable and battery for the short time necessary to charge (cheap and unlimited battery power). Want ANT+ and Bluetooth sensors both? You can do it - you can't with most GPS units. Want or don't want a ruggedized waterproof case? Take your pick. There are numerous mount options. If you are carrying a phone for emergency use anyhow (highly recommended), then you don't need an extra device.

So I think the phone world is going to do the disruptive technology gig on the GPS world in a big way. It's coming and the difference between them is really pretty minimal. The only reason I use my Edge 1000 now is that I like the Di2 integration and I like some of the Garmin software with Garmin Connect for keeping track of goals. But I have all the data synced with my phone and in Cyclemeter too. (Check out https://www.tapiriik.com for sync of pretty much all known data services). Looks like Garmin is going to turn the higher end units into sort of a bike server keeping track of ride data and with other sensors like their new rear looking radar unit/tail light that has promise.

J.

That's true in the same way that it doesn't make sense to have a car or a bike if you can walk.

not quite right. there is a lot more equivalency between a gps unit and a smart phone bike computer than with the examples you gave.

j.

You don't think cars and bikes have wheels in common? With the shared purpose of transportation?

Or are you being clever and agreeing with me because the negligible price difference between a phone and a GPS puts it in a different league from the difference between a $100 pair of shoes and a $30,000 car?

So you are saying that having a smart phone with you on your rides should just be used to make phone calls, if needed, and I should go out and spend $400.00+ on a Garmin or other GPS cyclometer or buy another phone with cycling software when both your suggestions do the same thing I can do with just my phone? I guess if I was the type of cyclist that wanted to "fit in" with the "In crowd" with the latest suggested gadgets from Bicycling Magazine or if worried about what other cyclists would say if they saw me riding without a Garmin, I could spend all that extra money to "duplicate" a service I already have but won't get to use.

What about tin cans with strings and smartphones? We can generate any number of bogus equivalencies but to what end?

J.

Not at all. I'm saying the GPS unit still makes sense for a lot of reasons even when you own a phone. I'm not saying anything at all about what you should do. Not sure how you got confused like that.

That's a funny objection on your part to my calling somebody out for making a false equivalence. Also, if you can't see the difference between a smart phone and a tin can with string, you shouldn't be taking part in these discussions.

No, that's exactly my point. I made a ridiculous false equivalence just like you've been doing but as an example. Thank you for illustrating the problem so well and for your agreement.

J.

I took the wire computers off my bikes that had them and run a free app called urban biker . If I ride over 20 miles I carry the phone in a top tube bag with a power bank and cord, That I have never needed . Here is why I went to phone app
1. Distance uses the same measure across all my bikes . The app I use I can set profiles for different bikes as long as it is close to correct mileage (close to 2 different wire computers) knowing it is the same distance on bike 1 or 3 or 5 matters more to me than being a 1/10 of a mile of in 10 miles .
2. less things to have with me/on bike
You can extend battery life by going to dormant screen and only running the stand alone gps and leaving andriod and google location services off. I just care about distance and average speed I don't watch speed while riding . Even if you want to watch the screen the top tube bag I have has clear plastic top. I can run with the screen active, have the phone protected and plugged into a power bank charging.
Roy