For a while now, I’ve been using ReQall to remember tasks that needed to get done. I tried using Remember The Milk but didn’t like that the iPhone app wasn’t free (you had to sign up for a Pro account). Now, RTM has decided to offer the iPhone app for use with free accounts but limited the functionality. The limits imposed on the free accounts are very similar to what you get for free from ReQall.
One thing I do like about ReQall (should I ever upgrade to Pro) is the integration with Evernote. I can add items to ReQall either by voice or text. I can follow my ReQall calendar in Google Calendar using the iCal URL. I can add items using the official Firefox plugin; RTM doesn’t have an official plugin.
One of the features I like about RTM is that I can tell it that an item repeats however often, in plain text, and it’ll recognize the time frame; ReQall only gives you a dropdown menu to choose from. RTM has a tighter integration with Google Calendar but I like being able to turn the calendar on/off when a day/week gets too crowded with appointments/tasks. RTM allows you to tag an item with a location, regardless of the account type; this feature is only available to ReQall Pro users. The free version of RTM only syncs once a day, whereas ReQall Standard syncs constantly.
They both offer something that the other only includes in the pay version, so I’m going to keep using both until I can decide on one over the other. If I ever do pay for one, right now I would pay for ReQall Pro.