It won't far outweigh it, it's more like 3:1 in favor of benifits.

Only 3:1, eh? Well, shoot. Actually, I think it'll be much more than that, but still 3:1 is pretty good.

So maybe the breakdown could be something like this: 

All based on mobile chipset cores (ala Snapdragon or ARM cores + SGX GPU cores) modified for gaming by Nintendo. 

1.) Portable Fusion Handheld (Spring 2016 Launch)

Quad-Core CPU/GPU, Approx. 250 GFLOP processing power, can handle ports of Wii U games at 540p resolution. 

2.5GB of RAM (1GB for OS, 1.5GB for games)

5.25 inch 1280x720 display (multitouch w/new rumble stylus). 

$199.99

2.) Home Unit Microconsole (Fall 2016-Spring 2017 Launch)

8-Core CPU/GPU, same as Portable Fusion, but overclocked. 

Approx 750 GFLOPS of processing power can run games at full 1080p w/anti-aliasing. 

4GB of RAM (1GB for OS, 3GB for games)

Ships with Pro Controller + Wiimote like remote controller (new designs)

$199.99

3.) Portable Tablet (Summer-Fall 2017)

9 inch LCD display

8-Core CPU/GPU, no overclocking. 

4GB RAM

$249.99

Same OS, same games, unified Nintendo Network ID for purchases. Same day releases for games ... ie: Super Mario Galaxy 3 launches and is available for play on all three devices. Cloud save transfers so you can play at home and continue play on the go seamlessly. 

http://www.nvidia.com/object/tegra-k1-processor.html
http://en.wikipedia.org/wiki/Tegra#Tegra_K1

Those are the specs for the tegra k1. It's highly possible to have a handheld more powerful than the wii u but I'm not sure how expensive it is at this point.

Another thing, I recall that Nintendo said that the Wii U would be the first or the example for this unified architecture. I'm not sure if that means the same line of chips, i.e. PPC cpu etc. or if that means similar memory architecture, or simply that the next systems will be fully backwards compatible with the wii u but not necessarily 3ds.

Ah ok, so it is highly possible that they would switch from their usual PPC chips and look elsewhere if it suited them?

I definitely agree. The more I think about this, the more I see how fantastic an idea it is. I personally think Sony will do the same. Think about it, Sony is already saying that the best part about the Vita, the part they're focusing on, isn't the individual games but the connectivity with PS4. Gaming of the future will use portable systems as mere portable extensions of a greater platform. Microsoft is moving toward this too with their integration of Xbox and Windows systems. See that integration with Surface they're doing with Xbox? There's your portable extension for Microsoft's platform. Gaming platforms will no longer be a single system, but a business platform built on multiple integrated systems and services. They already kind of are, this next gen will just finish the process by integrating the hardware systems.

But if it fails nothing would keep it afloat. I would hate to see that too because handheld and console gaming is completely different. By that I mean I'll pick up Animal Crossing for 10 minutes and be satisfied but want to play Mario Kart 8 for 5 hours a time. All I can say is that I'll sink a whole battery life into each time I play Smash Bros on both

Mario Kart's not really a good example of what you're saying since it's really just focused on a couple of rounds or one round and you can turn it off. Either way, I'm thinking there will be cross saves  and all that and suspend/resume on the handheld. That is a non issue.

Eh it was the first thing that came to mind. Also those tiny 3DS screens hurt my eyes after too long, but my TV size doesn't bother me with Wii U

Same here, I don't care for handhelds that's why the console would be for you.