Signal strength means nothing. Its like the silly bar codes on cell phones. You cannot compare between brands since they use their own standards.
If you can you want to test transfer rates between a wireless device and wired device in your house. The N transfer should be faster even in cases where it actually does have less signal strength.
When you test you want to go into the router and set the support to N only, the card cannot use any of the advanced N feature when the router must also support older b and g at the same time.
This alfa card is getting a little old, not sure why they have not come out with models based on newer chipsets.