What LPC122X development board/environment would you recommend?
I can't compare them because I've only used one, that being the LPCXpresso board and IDE (Eclipse-based). I'm well happy with both, the boards cost 20 Euro and the IDE is free for C, not for C++ although I believe it's easy enough to use it for C++, just not as turnkey as one might like.
I reckon the LPC1227 is roughly equivalent to the Mega1284, both are "just right" in terms of features IMO.
Rob