Stated with the evaporative vest, then the phase change vest.
The PCM vest will provide more consistent cooling than the evaporative vest.
Downside is they're bulky, only last an hour or so,
and requires another set of PCM in a cooler
recharging for swap out with the expended one.
Yes, it only takes about fifteen minutes to recharge in ice water.
Used mine for about two years.
Bought the Veskimo three years ago.
Started with the backpack cooling system,
then switched to the 9 quart two years ago.
Worth every penny.
The backpack lasts about two hours, the 9 quart a solid five to six hours.
Even if all the ice is gone,
the ice water is still about twenty degrees below body temp.
You'll know when the ice is almost gone.
It's very cool, but not cold.
I used my infrared laser thermometer
to check out the temperatures at various points on the cooling vest.
Readings were between 65 and 67 degrees consistently throughout the vest.
For me, it's effectively eliminated the decision point on whether it's too hot to ride.
Went out on Saturday and Sunday with temps in the high 90's with real feel up to 103.
Always ride with ATGATT and wasn't phased.
Went out for a ride at 1500, yesterday, just because I could.
Came back three hours later, just as comfortable as when I left.
Love the 9 quart cooler.
Hope this helps.
e-Mail Kurt, the owner.
Very helpful and informative.
Here a link to a previous thread: http://www.bmwlt.com/forums/showthread.php?t=46008