There may be some inherent advantages in pursuing the L-1 over the TN-1 including the dual-status implied by definition allowing for possible immigration to the U.S. There are many examples in the past along the Toronto – Niagara Falls ports of would be
TN beneficiaries routinely being denied entry due to displaying immigrant intent, including marriage to American citizens.
In contrast, TN does not allow for this and even though the recession has been declared over, the U.S. unemployment rate has yet to peak. Thus showing any kind of immigrant intent while attempting a TN would likely result in a denial in this kind of environment. Thus investigating the L-1 may be advantageous over the TN.
That might be starting to change again after reading the article located at:
http://www.americanlaw.com/immigrationblog/?p=33 If the U.S. economy ever catches fire again and starts cranking out some really good job creation, the way TN’s are interpreted might begin to change at the various ports.