Bullets are more hostile than the weather. A vehicle that allows everyone to have all around observation and the ability to quickly return fire rather than sitting inside a box being perforated by rounds while you try to egress is better.
In 2 RCHA we used to do winter exercises for three or four weeks under helicopters and without any vehicles. The strange thing is you become acclimatized to the weather. I found that coming home afterwards I'd be uncomfortable by the heat of the house while I'd been perfectly comfortable in an arctic tent. (Except the air mattresses - I hated those damn things - always froze my shoulder and hip)
There are always tradeoffs, but IMHO the ISV is a perfectly acceptable option to walking for that wheels-friendly European road network some of you keep touting. BvS10 for off road bush etc sure - but remember they come in at contract prices for an all up cost of just under $2 million each while these ISVs come in at around $0.4 million. I think for a UOR purchase - its pretty good.