I do not have experience with auto-renewable subscriptions, but I do have extensive experience with IAP and non-renewable subscriptions. I use non-renewable subscriptions for a service that isn't a digital download.
Renewable Subscription Cons
- User has to manually renew each month.
- You will probably want to consider longer subscription periods. My app has 2 month and 1 year.
Renewable Subscription Pros
- Users only pay for what they use. You can turn this to your advantage.
- My own app saw a good increase in conversation rates when I explained that subscriptions do not auto renew and so they did not need to worry about canceling the subscription.
- You can change the price!
- Much more flexibility about how you can use it.
- It has the standard popups during purchase. You will have a better conversation rate from the user hitting the buy button to them following through with the purchase.
Auto-Renewable Cons
- LOTS of regulations about what you can do with it.
- It is very possible that you won't be able to use auto-renewable in your situation.
- Only the user can cancel their subscription. You can't add an easy way to do this into your app and keep your users happy.
- The purchase process has extra steps that ask the user if they want to share their information with the publisher.
- There is no API to know when the subscription will end.
- You will have more negative reviews.
Auto-Renewable Pros
- Users don't have to manually renew.
- You have a more guaranteed income per month.
You will need to sync the subscriptions between devices. I use Parse.com as my backend. Basically, before making an IAP transaction as complete I push the data to parse. Users can then pull that data down onto their device to sync the subscriptions. Parse lets you save the transaction for users with and without accounts. So it has the benefit of giving you real time sales information.
EDIT: Auto Renewable Subscriptions will Change This Fall
Auto renewable subscriptions are drastically changing this Fall (2016). Pretty much every reason not to use auto renewable is going away. https://developer.apple.com/app-store/subscriptions/whats-new/