Best dipole wireless adapter to give me longest range?

I'm looking for a high quality dipole wireless adapter antenna for a laptop for this year at school. There are various wifi's all over campus.

I'd like to get the best USB dipole antenna that will give me the farthest range to have a larger variety of signals.

What do I need to look for? Does higher dbi mean further range?

I was considering this one,

Newegg.com - HAWKING HWUN4 Hi-Gain Wireless 300N Network Adapter IEEE 802.11b/g/n USB 2.0 Up to 300Mbps Wireless Data Rates WEP 64/128, WPA, WPA2, IEEE802.1X

But it's only 3dbi, (per their website) but I've seen other wireless adapters around 5 & 6dbi. I was looking for a 300mbps data transfer, but the 5 & 6dbi antennas I see are only 150mbps

But I want something just like the Hawking, just an antenna that plugs right in a USB port.

So is there a better option for further range than the Hawking?

Just out of curiosity, how much better are these hawking dish's?

Newegg.com - HAWKING HWDN3 Wireless 300N Dish Network Adapter IEEE 802.11b/g/n USB 2.0 Up to 300Mbps Wireless Data Rates WEP 64/128, WPA, WPA2, IEEE802.1X and WPS

Per their website that has a 6 dbi rating, but it's so bulky & cumbersome compared to just a usb dipole antenna.

It seems most of those are larger base sized adapters.

I'm looking for something like the Hawking HWUN4 I linked to that is just a small USB body & antenna & as low profile when attached to the laptop & for easy mobility

Is 3dbi really not that good? It must be much better than the wireless card built into the laptop isn't it?

as a ham radio operator there is NOT much difference between 3dbi and 5 or 6 dbi. you'll get a little more noise but that's about it. as for the speed that would depend on the connection itself not the antenna