In general Arduino definitely leads in documentation. The mbed community is smaller , but on the other hand more professional - so stuff would be of higher qual

In general Arduino definitely leads in documentation. The mbed community is smaller , but on the other hand more professional - so stuff would be of higher quality , less bugs , etc - but somewhat more complicated. Same goes for the tools - more complicated but more capable. If you're aiming towards something professional/startup/etc - mbed is the way .