First of all, while all wheel drive may help you gain motive traction during acceleration and may (depending on the system) help maintain neutral steering in cornering, it has essentially no effect on braking capability. All cars have brakes on all four wheels. Your Subaru should have anti-lock disc brakes all the way around, which helps prevent the brakes from locking into a skid by pumping the brakes at ten or more cycles a second (allowing the wheels to “roll” slightly and then brake, which has a higher coefficient of friction than continuous braking); however, if there is no traction between the tires and the street, there is no braking force, period. The assumption that all wheel drive will give you traction in all conditions is a misnomer that has led to innumerable accidents, especially on ice, snow, and unsealed dirt roads; the latter is the most common cause of accidents in Central and South Africa by aid organization employees driving AWD Land Cruisers as if they are driving around town in a Jaguar coupe, according to a professional offroad and evasive driving instructor I talked to a few years back. Or, as the Audi manual I read a couple years ago said at the end of the quattro all wheel drive system section, “The laws of physics still apply!”
As for the specific conditions; 1/2 to 1 inch of fresh snow on pavement is about the worst driving conditions next to ice and hardpack; it is just enough to create a crust of snowflakes suspended on a low viscosity liquid layer that is kept just above melting by the macadam of street pavement. Salting roads during snowfall can actually make this worse, as the layer will stay liquid at lower temperatures. You’ve basically surfing on top of the layer–like hydroplaning on rainwater, but even worse–until you slow to a crawl. If you’re sliding around in these conditions and going right through intersections, you are going way, way too fast for the conditions, and need to slow down or just not drive until the snow melts or is cleared.
Regarding tires: there is a wide range of capability in “all-season tires”, from basically just slightly better than summer use high performance to “suitable for snow if cautious”. I don’t know what the stock tires are on your vehicle, but recognize that OEM tires are selected generally for cheapness and compatibility across the vehicle line rather than for optimal performance, and so you may want to consider a different brand and make of all-season all-weather tires. I use a semi-premium (but not terribly expensive) brand of all-weather, all-season high performance radials on my car (also a Subaru) and haven’t had any problems driving through rain and light snow through mountains, although in those conditions I admittedly don’t try to drift around corners in an effort to replicate heart-pounding scenes from Frankenheimer’s Ronin. Tirerack.com provides some good, reasonably unbiased information and reviews on different brands of tires, including actual driving comparison. For the kind of conditions you describe, snow tires shouldn’t be necessary, and will create more noise and wear faster than all-season tires. Chains are unnecessary (and depending on your model, may not fit on your vehicle) unless you are driving on incline on hardpack snow, and will also tear the crap out of your tires if you use them frequently.
In summary, buy good quality all-season tires, slow down in snow and rain (if you think you might be going to fast, you are going way too fast), and don’t assume that the “AWD” badge and the marketing hype about Subaru Symmetrical All-Wheel Drive, Vehicle Dynamic Control, and “four channel, four sensor, computer-controlled, antilock brakes” is going to fundamentally change the laws of physics in the immediate vicinity of your vehicle.
Stranger