I’ve used both uIP and lwIP extensively.
uIP
- Great if youre only wanting something basic like a bootloader
- Small footprint.
- Uses polling so we’ve never got over 3kbit with it 🙁
- No DHCP ‘out of the box’
- Poor UDP support
lwIP
- Fully interrupt driven so much faster (~ x10)
- Includes DHCP with failover AutoIP
- UDP with multicast
- Plus more
EDIT:
And we’ve never used either with an RTOS as there has never been a need.