The 70-450 exam is the PRO exam while the 70-432 exam is the TS exam. In general, the PRO exam will be more focused on higher level skills such as design (choosing the right solution or technology) while the TS exam will be focused on more of the typical
day-to-day operations tasks. Look at the skills measured for each at the following URLs:
70-432
http://www.microsoft.com/learning/en/us/exam.aspx?id=70-432#tab2
70-450
http://www.microsoft.com/learning/en/us/exam.aspx?id=70-450#tab2
Notice how the 450 is focused on mostly design? While 432 has a lot of the operational tasks such as installation. In general, the PRO exams are geared toward those with more experience while the TS exams are geared toward those with a little
less experience. But be aware that the TS exams are not always (or even often) the easiest of the exams. I hear a lot of stories about guys that do a lot of design finding the PRO exams easier than the TS exams (mostly because they don't get their
hands on the operational stuff as often).
Good luck!
Brian
