There is not a MECA presence in Canada, they had an event director in Canada but well, the timing was bad. So this is probably a tough forum for an opinion.
I am the only person on this forum truely familiar with MECA (I think) since I am a MECA member. I have also done USACi in recent years and other organizations pre-IASCA. I am biased in favor of MECA, as I am a judge and soon an Event Director.
As an organization it is top notch. On the SQ side they have the finest SQ based program available, though I would never say anything negative about IASCA or USACi programs (they are very good too). The MECA SPL program is gaining in popularity and is very much worth consideration. The organization is relatively new but is as large as 'the big boys'. Frankly look over the rules of each organization and you will find each has positive points. MECA's US business model deals with lots of small shows, and a growing customer base. That seems to be consistant, an annual 10% growth rate in competitors.
MECA's greatest strength and biggest liability is that the competitors have the ability to change the rulebook (within reason) after each season. Not everyone likes change (especially when they are winning).
www.mecacaraudio.com is the meca website