Garmin or just use an Iphone?

Battery life is the biggest issue with smart phones.  If I go out on a long ride or long run, I don't want my phone to die in the middle of a workout.  And even if it didn't die during the workout...I still want my phone to have a charge in it afterwards...you know...so I can use it as a phone and brag on facebook to all my non triathlete friends what I just did.

I think you could do well either way with a 910xt or a dedicated bike and run gps device.  The edge 500 just came down in price to $160, so you could likely get that and a running watch for less than the 910xt if you are worried about issues with the 910.  I have one, and maybe I'm lucky, but no issues.  I do really like my edge 500 though and because I use power on the bike...I do find value in having a more dedicated bike computer (more fields available on each page).

I think a smart phone can be a good temporary or intermediate solution if you already own one...but I would not recommend buying a smart phone when one of the primary reasons is to use it as a GPS fitness device.  I do think that smart phones will eventually get closer to bridging that gap...but they need to solve the battery life issue first.

Our Edge 500 units work flawlessly.  HR, cadence, etc. and easily picks up power meter and downloads easily.  Both running kids have forerunner 10 units and they beat the hell out of my Timex GPS watch.

So..... 160.00 for Edge 500 + 100.00 for forerunner 10....260.00 and you'll have all the information you could ever want in a near error free package.

Yeah, the GPS tears through the battery rather fast. Haven't tried the newest phones with it out on something longer yet, but occasional use in apps has made a dent in a short time. I also got a dedicated unit (800 series) for the bike so that it would always have something with it. I don't want my primary communication device to be so exposed all the time. I still carry it with me, but as a back-up, so tucked away where it's covered up well and much more protected in the event of something happening. I went with the 800 (and now 810) because of the bigger screen for more info, but especially for the mapping. I'll go on rides that are mapped out ahead of time, and it's been very convenient to load these up and have the route immediately available to see.

Someday you'll be out there in the rain, or for longer than your iPhone's battery will last in GPS mode... or, you just might realize how handy it is to have numbers on your wrist when you're running.  There are many reasons why a dedicated device is just really handy to have.  Ruggedness, waterproofness, and many dedicated features of the various devices out there are just too good to ignore.

If I would recommend adding anything to your current iPhone solution- it would be to purchase a HR monitor.  bluetooth, if you want it to work with your phone, but Garmin's and most others operate on ANT+.

I used a garmin watch for both running and cycling for quite a while- but when I broke down and got an Edge 500- it was just so nice to have a dedicated spread of variables in a cycling dedicated device.  Eventually- I wanted something to count my swim laps and picked up a swimovate for $90- which worked fine.  As much as I loved my garmin forerunner 405 running watch- I went through 4 of them in 3 years due to reliability issues, and it was constantly freezing up on me. Now, more recently I updated my Garmin 405 running watch with the Suunto Ambit 2.  I'm thrilled with how versatile and completely reliable and stable it is.  Great for the swim, terrific for running, as I use its navigation capabilities, yet, I still use the 500 on my bike.  

There is no right or wrong here.  It just depends on how much money you want to spend on having a trick new device.  Personally, if you can swing it financially, I'd recommend quite a few of them.  And, while the gamins are great, and there's nothing out there with the features of the Fenix 2- it's not yet the most stable unit.  You might want to consider the Ambit 2- which is very solid.  Or, the New TomTom's, while perhaps not any more stable than the Garmins, are cheaper, simpler to use, thin and now with the HR integrated into the wrist band- they are offering some compelling products with a great future.  TOM TOM is still updating the firmware.  

Competition has been a great thing for us data geeks.  Lots of cool products out there.

I am in the same boat currently. I already had an iPhone 4s so I decided to give that option a try. I picked up a Topeak stem mount for the phone that works great.

Biking: The battery life can be an issue, my phone already has weird battery quirks so it may just be me, but it can last long enough for a decent ride. I rode 4 hours on Sat and it worked fine. One issue is if you ride into an area that does not have good cell reception your battery will die quick. Also you have to leave the screen off to keep the battery alive so no speed or distance updates. I have a riding buddy that uses the 4s and says he has used it on 8-9 hour rides without issue, but again, no screen. The Topeak mount comes with a rubber phone condom, I would advise using it if you sweat a lot, sweat on the phone will get into the home button and kill the phone.

Running: Strava always thinks I have gone farther than I actually have. Sometimes a little, sometimes more. I now run with my 305 for decent data and let the phone track in an armband so I can upload to Strava, phone always has me going at least a bit further. 

So for me, the phone is not a great solution for anything really. Constant battery worry sucks on the bike, not having a readout kinda sucks, etc. I do like having the phone mounted to the stem in case the wife texts or calls. 

Ideally for me I would have the Garmin Fenix 2 for running, swimming, mtb'ing, etc. And then a dedicated Garmin 500 or 800 for the bike. But that is a good chunk of change. I will most likely be going with the Fenix 2 in the next month or so and I will wear it on my wrist for the bike. I want something I can OWS with and I like the idea of tracing my entire IM with one device. I chose the Fenix over the 910 because of the features and I like that I can wear the Fenix for everyday use. Also I like to set my truck as a waypoint when I go hiking/hunting, I can do that with the Fenix and not have to carry an etrex.