My only concern with the Mackies is that it seems their quality control has really suffered in the last few years. I've got some stuff from 10 years ago or more that still work great....
But, for my job, I recently purchased some PA speakers, personal monitors and a mixer....and each piece with the exception of one PA speaker has exhibited problems of one kind or another....(some more serious than others, but still...)
It may just be the luck of the draw on my part...but enough to give me pause.
I've also read some not so great reviews on them (not about the sound, but about the physical issues...sound dropouts, overheating, poor QC, etc)
My guess is that any speaker made in China (including the Yamahas) are going to potentially have all of these same issues...but with the Yamaha's I haven't found nearly as many..
(Personally, I do like the sealed box monitor, as Bit made mention of regarding the Mackies....My Hi-Fi speakers are sealed, and the subs I use have a passive radiator, rather than a port...and, I have to say, they sound awesome)
Sometimes I wish there were just one set of Monitors available....it'd make the choosing process a whole lot easier ;)