If it is your only intention to read PDF files, then it is "no contest".
I have always used Foxit. It runs without bugs in Vista also. When you click on a PDF file, on the net or on your HD, it opens instantly, unlike that long wait with Adobe.
P.S. Don't forget Avira(anti virus) free edition in the list of up and coming programs. It came out top in the detection rate for free programs. I had always used AVG but thought I would give Avira a whirl. I run a clean computer and do not normally visit virus prone sites. To my amazement, Avira found two trojans on my computer, undetected for four months by AVG!