Upgrading from A77: Go with the A99 or the A7R?

*Some of the content of my question will be obvious or needlessly explained to users in this forum. I am pasting this question several times in many places to get a good number of replies and not all readers will be as familiar with Sony cameras*Question or opinions about upgrading: A99 or A7R?Background: I currently own an A77 with some good A mount lenses, and although I am not technically a professional, I create professional level images and am moving forward to making this my career. I am interested in doing advertising and event photography (not including sports), and will undoubtedly continue with weddings and portraiture.My priorities in order of relevance, all are important:1) Durability and long term cost effectiveness.2) Focus speed and accuracy.3) Resolution (although I feel 24MP is acceptable, 36 would be nice. More is unnecessary for my needs.)4) Low noise issues at all ISOs, and low light performance.Video performance is not currently on my list of concerns, I can address that in the future if I find myself going in that direction.Summary:The A99 has A-mount (which is all my lenses) and is a very good camera, but showing its age a little at 3 years old. The advantage is that I will have better focusing capabilities and way more lens selection, in addition to using my A mounts natively, which I think is a better mount because, by virtue of size, it allows for larger apertures. The drawback is that it's an SLT meaning that it's mirror lets most of the light through while using a little reflection for focusing and metering. Great camera though.The A7R is much newer and uses an E mount lens. I can get an adapter to use all of my current lenses but will lose focusing speed and precision unless I invest in the (as of now) limited and expensive E mount glass. It is a lot newer and has some amazing features, but the biggest difference is that it is mirrorless. Focusing is slower but still acceptable for most shooting. It has a higher resolution (36MP vs 24MP) but this is not much of an issue as 24 is plenty for pretty much every print I will make. Low light shooting is better, and its much smaller, and has wifi and Bluetooth technology so I can upload immediately to social media. Also an amazing camera.Which direction do I move in? Stick with the A mount and have better focusing ability or go with the E mount and gain a little resolution and technology? There are other concerns too like battery life and memory but these are not as important to me.

I can't comment on whether you should upgrade a Sony body to another Sony body.

I can say this, having just rented a D810 (36MP) for a week. You don't need 36MP unless you are creating very large prints. 24MP is plenty. I will posit that, if you currently have a 24MP sensor and think you need more, then you may not be taking full advantage of what you already have available to you. (Many professionals have done exceptional work for a very long time with half that resolution.) Having tried out 36MP, I won't be purchasing at this time.

Low-light performance, auto-focus speed, lens mount: those are important points to consider. 

All IMO, of course.

Biggest advantage of mirrorless is the what you see is what you get viewfinder. The A99 and A7R are both very good cameras. I would handle both to see if I had a preference. I personally would go for the one with the lowest noise at the highest ISO.

A7r II

E-mount is Sony's future.  Their E-mount lenses are really great.