Two key criteria for a tyre are
1) A rubber mix defined for good grip in the expected temperature range - true "summer" and "winter" tyres operate best in their design ranges - summer tyres are too hard in the cold and lose grip - winter tyres are too soft when hot and may not grip ideally and can wear badly. Cross climate tyres use a compromise compound that works well in temperate climates and also appeal to SUV users
2) Tread design - lots of blocks and/or channels help water dispersion to prevent aquaplaning and help grip in snow/mud - so winter tyres have lots of blocks/cuts - these blocks move around and get hot when going fast so winter tyres are often speed limited. Cross climate tyres have tread designs closer to winter tyres so are often good for wet grip/aquaplaning.
Our M3W (like many others) has a cross climate on the rear for confidence on wet grip - on our Boxster we go all the way with 2 sets of wheels for summer/winter. Suspect in our climate neither get tested to the limit but on this kind of safety issue, caution is good.
However, biggest concern for me is usually the way people run their tyres all the way to (and beyond) the 1.6mm legal tread limit let alone to the typical 3mm wear indicators...this has biggest negative impact on wet grip/aquaplaning - we usually change well before the wear indicators and this also ensures the tyres are not too old (5-6 years seen as max recommended as rubber hardens over time)
