ISO Recommendation Winter Tires + Rims

It definitely comes down to tradeoffs. If I lived in Portland, I would go for Michelin X-Ice's as others have recommended. They have great winter performance, are widely available, are a good value, and have a 40,000 mile warranty. Blizzak WS80s are also good, but don't seem to last as long (I had the WS70s, the previous model and they did wear very fast despite the fact I never used them in spring or fall).

If you want even better winter performance, there are studless Nokian winter tires that outperform them in the snow, but you'll most likely pay more for them. Unless you find a deal, not worth the little bit of extra performance for the cost unless you really live in harsh winter conditions (eg. Alaska).

The weight of the wheel will have little impact on snow handling driving. The tire width and depth will. Generally for maximum winter grip, you want wheels that are an inch or two smaller than factory and 10-30mm less wide, but are approximately the same overall diameter. This is because you want as much tire depth as possible to flex over snow/ice imperfections and thinner width tires, which apply more pressure per area to dig down into slush/ice/packed snow/etc.

Reference: https://www.tirerack.com/tires/tiretech/techpage.jsp?techid=126

Note: In very deep snow, wider than factory tires is actually better, but in snow that's deep enough for the bigger tires to really be an advantage, your bumper won't be clearing the snow in a Prius anyway, so you wouldn't be going anywhere regardless.

Michelin X-Ice 195/65R15 might be your best bet.

 

Typo: "225" should be "215"?

That's an Uber/Lyft stipulation? That's a pain, and will be expensive, both initially, and ongoing: every time you swap you will need either the dealership to intervine with Techstream (at $75 ~ $125 per pop), or really knowledge up, and invest in some not trivial equipment for DIY.

Why on earth would they not recommend 195/65R15? Doesn't seem like very good places.

Yes.

Funny thing: the Corolla rims I'm using seem neck-and-neck with the stock 15" alloy rims, for weight. They are definitely a lot lighter than my third gen 17" porkers, as my back can attest. These are the rims:

Corolla steel rim, part no: 42611-02471 (2003-2008 corolla or matrix, CE, LS, S)

 

There's no problem going from a stock 17" rim to 15" on 3rd gen; I'd suspect similar conditions apply on 4th gen, ie: the brakes, wheel hubs, anything near the wheels, is identical.