Seriously, a better machine? For some people, including myself who use a retina display iPad, the rmbp isn't a big deal. Having an Ethernet port, the ability to upgrade, an anti-glare screen, a slot lock is. At least it was for me.
I could have spent the same amount of money on a 2.3 rmbp with 16gb as I did on my 2012 2.6. But I considered the unibody a better machine for my use. If I need retina I'll use my iPad, if I need power, I'll use my 2012 unibody.
The RMBP has an ethernet port. You just need an extra cable. You can get 16gb for your RMBP if you want. I doubt you will ever 16gb in the next 5-6 years. Furthermore you can get a 768gb ssd and btw the ssd is also replaceable. So the ability to upgrade is a moot point. And what is a slot lock? Do you mean those kensington locks?
I am sorry but I think you made a stupid mistake by buying the old MBP. There just is no reason to get it. And your ipad comparison doesn't make any sense at all. First of al the RMBP is a notebook with a full fletched OS. The ipad is a 10 inch tablet. The RMBP has a bigger screen and is the more productive machine of the two. Anytime you are using your notebook you are going to benefit from the retina screen.