And this is the output....

I'm glad you got it working!
Try experimenting with glDisable(GL_BLEND) and see if it still works (unless your intention was blending the background with what was already rendered there).
I think my advice earlier was wrong and you only need the test, without blending.

you didn't see the link I've posted
Sorry. You posted a link to a page with one paragraph of title text and some embedded rectangle that doesn't work without JavaScript. Okay, I temporarily enabled JS for slideshare.net and slidesharecdn.com. And what I see?

A veritable wall of sites that suddenly want to run their JavaScript in my browser.
How about NO?
I alvays ignore such dumps of websites full of suspicious third party scripts.

Added this to my hosts file:
Code:
127.0.0.1 www.slideshare.net
127.0.0.1 slideshare.net
127.0.0.1 slidesharecdn.com
127.0.0.1 public.slidesharecdn.com
so that that dump is always blocked.

Besides, judging by the title that was something a nVidia dev said 9 years ago. Lots happened since then and I am more interested in the situation of today.

On most desktop hardware we've done testing happens actually the opposite - glBegin/glEnd is close to performance to glDrawArrays
That's a very interesting result and I can't wait until I'm done with my rehaul to do some more benchmarking.
There must be some interesting dependency on driver version, operating system, the way you initialize GL or even if your app is 32 or 64-bit.
Because I got what I got, both on Win7/HD3000/i5 and Win10/GTX460/Phenom II.