Can you tell the difference between SOCs? (Why OEMs and not cores matter)

I have been using the Nexus 7 for awhile now and I can't say that I am impressed with the speed. I think it's much better than the Kindle Fire tablet in terms of build but I really don't think the updated internals are making much of a difference. I am using the Nexus 7 bone stock but here's a screenshot of what I am seeing a lot:

Screenshot_2012-08-08-18-01-55_medium

via lh4.googleusercontent.com

In a lot of ways my OMAP dual core devices are actually performing better than my Tegra 3 device. I have a Droid 4 that I run on 2.3 (now on 4.0) and it is running much smoother than the Nexus 7 that supposedly has better specs. Even the Kindle Fire which only has 2 cores feels quicker in loading up certain webpages and using apps like Facebook.

My feeling is that it is more than just about cores OR Android version. I have had the best experience so far using TI OMAPs and the worst experience using Tegra chips despite the Android version. I know this is just anecdotal but I'd like to hear you guy's experiences.