Purchase Decision: OM-D EM-5 or K5II

I just know I'm suffering from "analysis paralysis" as someone stated in a different purchase decision thread, so I'm hoping someone here can give me some objective advice. As you can see from the title, I'm struggling with the decision of purchasing the OM-D EM-5 or the K5II. I know both are different cameras (micro4/3 vs. APS-C) (mirror-less vs. DSLR) but I've managed to narrow the field down to these two options. I'm not against Canon, Nikon or Sony so feel free to add to my confusion if you have better suggestions for my intended use.

Some background: I recently sold my Pentax K7 in preparation for this upgrade because I haven't been satisfied with the low-light performance. I have a Canon S95 P&S that takes way better indoor, low light photos than my K7. Of course, some of this can be attributed to the kit lens and not making an investment in some fast primes or fast zooms, however, I also know that the K7 sensor just isn't as good as what's out in the market today. I'm a 'hobbyist' but still on the entry side of the hobby. I feel I have a good grasp of composition and exposure, most of which I learned from trying to push my K7 to do more. I mostly take family photos (2 young kids) and candids, with the occasional family gathering, wedding, etc. along with taking an interest in landscape photography, nature and astro. Now, I know that's a wide spectrum of interests but as I said, I'm really entering the hobby and haven't found that niche yet so I'm trying to keep my options open. Sorry, that was a bit long winded to getting to the point of my main requirements:

• weather resistant
• excellent low light / high ISO performance
• support for wireless, external flash at some point (knowing some times flash is needed)
• good selection of lenses (15mm, 31mm, 70mm, fast zooms)
• $1200 - $2000

I'm sure there are more but that's the basic parameters for my search. Here are the two configurations I'm looking at putting together, both of which are at the top of my budget because of the lens choice:

1. K5II with DA*16-50 - $2000ish (lens price on Amazon was at $979 new)
2. OM-D EM-5 with Panny 12-35mm f2.8 - $2000ish (B&H pricing)

With either camera, I figure that I'd need a longer zoom at some point and one or two fast primes.

So, is there anything comparison-wise between APS-C and micro4/3 that should sway my decision one way or the other? And by that, I'm not speaking of size/ergonomics of the camera but overall IQ and performance / bang for the buck? As I said, I'm not a pro and realize that the camera is but a tool and it's the person behind the camera that makes the biggest difference, however, I want to ensure I'm not missing something in either of these choices. If I should happen to get that 'perfect' picture, I'd love to be able to print on 11x14 or whatever the largest medium possible based on the camera I choose. (note: this doesn't mean I want a FF camera, it just means I don't know what print limitations are with these two cameras, if any).

Thanks for your time and input!!