Part of your problem may be that you USB device is not certified to the standard. It says it conforms to a "draft"..ie prestandard version of 802.11n. Hard to say if this is just a old device or if they are being cheap and not paying the license fee.
You will not find a lot of difference between USB sticks. The ones that tend to work a little better have external antenna that you can replace and have a long USB cable that allows you to place the device on top of the case. It depends what your priorities are, if it being small matters then you will have to live with slightly poorer performance.
Almost all the newer stuff is certified standards so they all pretty much work the same. Before the standard was finalized you had lots of differences.