I am going to develop a online document viewer. There are two most popular way to do it. One is the traditional flash way using pdf2swf.exe and flex. The other is a newer way using HTML5 and js based on the opensource pdf.js. I am wondering which way is more reliable and efficient. Since the html5 and js way is a lighter way but the process is heavily relying on JS which seems not really efficient and not better supported by browser such as IE 8 (which is used by some our clients). We not really care about the SEO problem therefore, flash way seems more appropriate.
So please help me compare these two approach and is there any other better way? My purpose is to simply display and preview the document.
Btw, I looked at the groupdocs as well since is not a free services...but it is still can be considered.