Because I'm rather tired of MLS being called bush league and think Mexican league is all this and all that.

Don't get me wrong. The Mexican domestic league is the better league than MLS right now. But I think MLS will be better maybe in 5-8 yr frame. Here's my reason why.

-Potential for more money in MLS than FMF
By wealth comparison, Mexico will never be as rich as US. While MLS has to fight against other major sports leagues for money and exposure, the potential for more money is present in US market.

-Potential growth of audience in US
It's no secret that soccer fans in US is growing, starting with grassroots/youth football to World Cup finals viewing of 25million or something. More soccer fans equals more money into league equals better quality product on field.
While in Mexico, soccer is already number one sport, and there's limited room for growth in audience.

-Possibility of expansion
Mexico is pretty much tapped out for expansion of new teams.
MLS is going strong with Portland, Vancouver and Montreal, 3 potentially strong markets to join in future, with room for even more growth, to possibility of creating a 2nd tier league (a la USL) or even third tier (a la PDL)

-Star power
With signing of Beckham, MLS has gained enormous exposure all around the world. This has translated into MLS being able to attract better foreign players, not just in their retirement age as in the past, but those still in their prime.
It's huge that players like Thierry Henry and Rafa Marquez turned down interest from EPL and other European teams to come to MLS. Marquez reportedly turned down offers from Mexican teams to join MLS.
With players like Nery Castillo (another Mexican star btw), Omar Bravo (formerly a Chivas Mexican start), even guys like Boskovic, Mista willing to give MLS a shot, MLS has been able to attract more variety of foreign players. While Mexican league has stuck primarily with Hispanic/South American. This is probably due to no language barrier between Hispanic countries. However, US offers better quality of life than Mexico. Trying to raise a family in Mexico right now... It's not a pretty thought.

-Emergence of US domestic players
With better performance of USMNT in World Cups, you notice the quality from individual players since 94 WC. While there are definite gaps in youth programs and quality of coaching at all levels, this is improving, as more money is invested into training and youth academies.
Better US domestic players translates into better product overall for MLS.
It remains to be seen just how much more money is going to be invested in Mexican leagues, and if Mexico's performance in World Cups are any indication, there seems to be a stagnation.

I'm excited for MLS, because I see a lot of potentials. Of course there is always room for improvement and the quality isn't quite there yet, but I'm happy the direction MLS is going, and I really believe that MLS will be the best domestic league in CONCACAF

/rant