It's not really not showing or slowing down (some text on BOTH the iPad and the Nexus don't show - so I think it is the power point itself.)
For PDFs on the Nexus, I found a very nice reader for it, but yet to find a power point reader that is smooth (so I don't need to convert the ppt to pdf) vs the smooth iPad - but I haven't found a nice offline option for power points on the iPad.
To be honest I was in a similar situation once pertaining to mostly PDF files.
I went with Android because I'd need to email multiple PDF files in a single email. Android made it easy and it's not really possible to email more then one PDF at a time on iOS. This was years ago but I believe it's still the case even today.
I used an iPad for web browsing and such and an Android tablet for work. Now with iOS 7 on newer iPads even web browsing is unstable. Apple, particularly iOS devices really lost their charm and overall usefulness for me.
I still use an iPhone. But even that I've been toying with switching to Android for a device that can keep up with my work flow. I've spent too much time waiting for the next iOS devices and versions of iOS....