Dream spark licences only last as long as your a student. ( dream spark is msdn for students) if you know you like windows 8 and will want to keep it. I would say spend the money now save a reinstall later. Plus if your device is 64 bit compatible I would always recommend using 64 bit because it has its advantages. The best been no ram limitations ( 32bit can only use 4gig)
And application address space ( again in 32bit limited to 4gig) so if you use big memory heavy programs 64 bit will always be faster.