TN vs Practical Training and taxes

Hi,

I have read the previous posts but still need clarification on the pros and cons of TN vs F1 CPT/OPT.

I have been a graduate student for more than 5 years and thus pass the substantial presence test. I have yet to submit my thesis but have a temporary employment offer. I will submit my thesis in a month and have been told I can do this while on a TN. I can use CPT/OPT for my job or I can apply for a TN visa. If I use practical training, I need to pay tuition to my school (expensive). My criteria for the decision are cost and ability to get a green card at some point.

It seems to me that the taxes are the same (social security and medicare) if you are on a TN or are on CPT/OPT and meet the substantial presence test. Is this correct? This makes TN more attractive since I won't be paying tuition.

I guess one advantage of OPT is that it lasts for more than two years in my field/with my employer, giving me plenty of time to get an H1. I will have a PhD by the time I apply so I think my chances of approval are fairly high. On the other hand, it doesn't seem like a problem to apply for an H1 while on a TN as long as my TN is valid. My current offer is temporary but if it is extended, I can apply for another TN in say Mar 2010. I guess I can apply for the H1 by the April deadline in 2010 and hopefully get it by October 2010? If I don't get the H1, I should still be able to work on the TN until the following March, right? I head that the job description for the H1 application must be different from the job for which the TN was granted. I would be applying within the same company throughout.

Are there any reasons why a TN is *not* a good idea given that I can use OPT?

Thanks!

Tax-wise you can't file 8843 if you've been there more than five years so it makes no odds, the tax situation isn't affected by your immigration status.

OPT is definitely the better option, imo. Because you apply for it yourself and your employer is not involved at all. And if you need to switch employers or get another one, all you do is fill in an I-9 like everyone else does.

No point going through the hassle of TN-1.