I'm glad the adobe site helped. I used to download courses from MIT's open course ware and it made me want to chuck my laptop through a window when all the lecture notes were in pdf format. I discovered that and fell in love. 
To answer your question:
zoomtext is much easier to -learn- to use. It's pretty much install and select the power you need.
Braille displays require some learning at first (something I don't think should take casual web users more than a month or so to get down, especially for those who are already very good with braille)
Your speeds at first probably will be considerably slower than whatever you work with in Zoomtext, unless you happen to run it above 9-10x, in which case it's comparable or faster during the first few uses. You'll finally start experiencing -really- inaccessible web sites probably more than you did with zoomtext, which can be a disadvantage.
On the other end, reading documents or even books through sites like bookshare.org is made super easy. I found this one godsent, as I stopped having to deal with the ever popular "paper jammed" my printer loves to inform me of.
For many people, zoomtext is the ideal option (because they don't want to deal with navigating braille, can't hear/don't like listening to content, or just because they have enough usable sight for that to be clearly better) But for alot of others I know who started using readers and braille displays over magnification, the answer is a strong "I wish I'd stopped clinging to my vision a long time ago."
