Usually when there is a big (suspicies) discount you can expect two things:

software company will be acquired by a bigger one;
new version will come;

I have never seen such a discount at modo; that's why I vote for the first one otherwise we are still in eco crisis.

But I can suggest a better thing: for 550 you could buy a better computer with a GT 670Ti for cycle render

I felt these same feeling you want to buy an original and professional software that is valuable for a reasonable price after you can talk to yourself that you are a very CG professional because you spent a lot of money for a software. You will be the same good professional if you use Blender that is also same and professional however extra cheap. and? Buy If you think you will be more productive with modo.