Montbell makes several nice windshirts that make deciding a tough choice. Basically you've got:
Tachyon Anorak - 7D Nylon, Hood, Pull-over, Drawcord hem & hood - 2.3oz
UL Wind Jacket - 15D Nylon, No Hood, Full Zip, Elastic Hem, Shoulder Pkt - 2.6oz
UL Wind Parka - 15D Nylon, Hood, Full Zip, Elastic Hem, Shoulder Pkt - 3.3oz
The Tachyon Anorak is the lightest, but I opted for the UL Wind Jacket because I get a bit more durability and a full zip for just 0.3oz more. I rarely use hoods. If you do want a hood, then it's basically a question of if you want to add 1oz in exchange for a little more durability and a full zip.
GoLite's doesn't list the denier of their Dakota windshirt but they do list the nylon at 48g/m2 which is 1.44oz/yd2. I believe Montbell's 7D nylon is roughly 0.75oz/yd. Most likely the Dakota uses 30D nylon. If this is true, then this option breaks down like this:
Dakota Windshirt - 30D Nylon, No Hood, Pull-Over, Stows in Pkt, 3.6oz
Your preference of fabric denier (durability vs. lightweight and cooler) is likely what should determine the ideal windshirt for you. The GoLite one is a bit heavier mainly because it uses 30D nylon. 30D nylon is still pretty lightweight and it's considerably more durable than 7D or 15D. If you're going to be bushwacking or sitting around sparking fires then the 30D is a good choice. If you're mostly concerned about not getting too warm on hot days, then a Montbell one is likely the way to go. For comparison, most sleeping bags use 30D for their shells.
I personally suggest buying whatever option you think will suit your hiking best (as opposed to deciding based on price). I wouldn't buy the GoLite one just because it's a bit cheaper if it's not what you really think is best. The price difference isn't that big....40% off of $80 is $48 (GoLite) and the Montbell ones at 20% off are $59-$71.
EDIT: Regarding that GoLite wisp windshirt. GoLite's website rounds to the ounce, so to really get an accurate weight you need to look at the grams and convert to ounces. So the Wisp is really 3.2oz and the Dakota is 3.6oz. I think these shirts are basically the same but the Wisp is the older version. GoLite recently changed a lot of their stuff to use recycled fabrics which are slightly heavier. The extra 0.4oz of the Dakota is likely due to the recycled fabrics and because the zipper is longer. If you can find a Wisp then go for it, but GoLite probably won't be making them anymore since I believe the Dakota has replaced it.
Too bad the price went up from $50 to $80. Maybe have a look online at some other retailers that sell GoLite. Perhaps one of them has it in stock. Even full price is basically the same as the Dakota at 40% off.