get the Best Camera of the Year 2013. wont go wrong
Sony A7/ Sigma 19-2.8 E/ CV 35-1.7 ASPH/ FE 55-1.8/ MC Rokkor 58-1.2/ Pentax SMC K 135-2.5
Streets/Food?? - Pentax Q7
All the cameras can do what you need/want.
The A7 will have a larger file that can do very large prints (but are you doing them?)
It will also have better high ISO performance, more DOF control, DR and more robust files for post processing.
However, buttons are not that well laid out (and cramped), native FF lenses are just coming out and really limited in selection.
ATM, I'd say that its a manual lens users best bet as a digital FF camera, but not ideal for someone relying on all AF lenses.
There is an adapter for A mount lenses, but imo, its a bit too clunky. YMMV
The other 2 are both m4/3 cameras.
Niffy handling and AF speed.
Nice range of lenses, but imo generally sharp from wide open in the centre, more reliant on software correction of distortion and many lenses have less sharp edges.
Files break up more easily with post processing (esp. landscapes) (not a deal breaker if you do little of it)
All are good choices.
You need to determine what is important to you.
The EM-5 will be a better choice to start from. most newbies to photography have no idea how to handle the Depth-of-Field or get overwhelmed by the controls of a Full-frame system.
not saying that you'll never get used to it, but a simpler, more basic camera to start with will be better.
not forgetting that the A7/A7R requires a higher budget to start with: you need a basic flash (F20M) and a good lens.
even the A7R's 36MP sensor is tough for some seasoned hobbyists to handle.
In the end, good photos is about content. The technical stuff is secondary to that.
Get the camera that best suits what you want to achieve. With modern day cameras, the gap between different systems are narrowing very fast. For 99% of users, any current camera models will work fine.