You won't notice any difference especially comparing the same two tires just in the different sizes.
Any tire with a taller sidewall will ride nicer but the minimal difference in these two tires could simply been a supply chain issue during manufacturing so both had to be listed.

 

If I remember right the 175 came on the lower trim and the 185 came with the LE.

I believe your speedometer will be more accurate with the 185s. It's a few mph low at hwy speed with the 175.

 

I run 185 summer and 175 winter have been for 7 years no issue. Smaller tires width carve snow a bit better is my logic. I've also never bought a brand new tire my whole life so whatever best available used at the time is what I go with. Very important to get fresh tires with a fairly recent date stamp makes way more difference than the 1cm difference even brand new check the tire date and don't accept old rubber.

 

difference is minimal, but yes 175a equate to better snow carving, and the 185s better warm handling (plus it looks bigger). What size is your spare? if its a full size then stick to whatever size that is.